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$ 550,614

$ 527,873

33,435

37,535

(704)

(619)

(1,269)

(880)

$ 582,076

563,909

Temporarily impaired securities, Number of Investments | Investment

207

Temporarily impaired securities, Less than 12 months of temporary impairment, Estimated Fair Value

$ 244,340

Temporarily impaired securities, Less than 12 months of temporary impairment, Unrealized Losses

(642)

Temporarily impaired securities, More than 12 months of temporary impairment, Estimated Fair Value

9,494

Temporarily impaired securities, More than 12 months of temporary impairment, Unrealized Losses

(62)

253,834

Available-for-sale securities [Member]

(704)

534,029

510,184

304

347

(704)

(619)

Available-for-sale securities [Member] | Debt maturities of one year or less [Member]

533,629

509,912

304,150

179,659

203

109

(150)

(71)

Available-for-sale securities [Member] | Debt maturities of more than one year [Member]

304,203

179,697

229,879

330,525

101

238

(554)

(548)

Corporate debt securities [Member]

$ 229,426

330,215

Temporarily impaired securities, Number of Investments | Investment

178

Temporarily impaired securities, Less than 12 months of temporary impairment, Estimated Fair Value

$ 165,321

Temporarily impaired securities, Less than 12 months of temporary impairment, Unrealized Losses

(397)

Temporarily impaired securities, More than 12 months of temporary impairment, Estimated Fair Value

9,266

Temporarily impaired securities, More than 12 months of temporary impairment, Unrealized Losses

(15)

174,587

Corporate debt securities [Member] | Debt maturities of one year or less [Member]

(412)

205,973

^[1]

142,096

^[2]

153

^[1]

^[2]

(67)

^[1]

(27)

^[2]

^[1]

^[2]

Corporate debt securities [Member] | Debt maturities of more than one year [Member]

206,059

^[1]

142,144

^[2]

148,079

265,969

177

(345)

(393)

Debt securities issued by U.S. government agencies [Member]

$ 147,789

265,753

Temporarily impaired securities, Number of Investments | Investment

Temporarily impaired securities, Less than 12 months of temporary impairment, Estimated Fair Value

$ 56,358

Temporarily impaired securities, Less than 12 months of temporary impairment, Unrealized Losses

(167)

Temporarily impaired securities, More than 12 months of temporary impairment, Estimated Fair Value

Temporarily impaired securities, More than 12 months of temporary impairment, Unrealized Losses

56,358

Debt securities issued by U.S. government agencies [Member] | Debt maturities of one year or less [Member]

(167)

51,021

^[1]

23,242

^[2]

^[1]

^[2]

(35)

^[1]

(16)

^[2]

^[1]

^[2]

Debt securities issued by U.S. government agencies [Member] | Debt maturities of more than one year [Member]

50,999

^[1]

23,248

^[2]

55,525

41,308

(132)

(127)

Debt securities issued by the U.S. Treasury [Member] | Debt maturities of one year or less [Member]

55,398

41,184

9,022

6,239

Debt securities issued by the U.S. Treasury [Member] | Debt maturities of more than one year [Member]

$ 9,040

6,245

9,062

Debt securities issued by states of the United States and political subdivisions of the states [Member]

9,083

Temporarily impaired securities, Number of Investments | Investment

Temporarily impaired securities, Less than 12 months of temporary impairment, Estimated Fair Value

$ 22,661

Temporarily impaired securities, Less than 12 months of temporary impairment, Unrealized Losses

(78)

Temporarily impaired securities, More than 12 months of temporary impairment, Estimated Fair Value

228

Temporarily impaired securities, More than 12 months of temporary impairment, Unrealized Losses

(47)

22,889

Debt securities issued by states of the United States and political subdivisions of the states [Member] | Debt maturities of one year or less [Member]

(125)

38,134

8,082

(48)

(28)

Debt securities issued by states of the United States and political subdivisions of the states [Member] | Debt maturities of more than one year [Member]

38,105

8,060

26,275

14,186

(77)

(28)

Equity securities [Member]

26,239

14,195

16,585

17,689

33,131

37,188

(1,269)

(880)

Equity securities [Member] | Securities included in other current assets [Member]

48,447

53,997

1,269

1,538

1,021

618

(1,269)

(880)

Equity securities [Member] | Securities included in deposits and other assets [Member]

1,021

1,276

625

Equity securities [Member] | Regulus Therapeutics Inc. [Member]

625

15,316

15,526

32,110

36,570

Amount of transfer between Level 1 and Level 2 investments

$ 47,426

$ 52,096

[1]	Includes investments classified as cash equivalents on our condensed consolidated balance sheet.
[2]	Includes investments classified as cash equivalents on our consolidated balance sheet.

Fair Value Measurements, Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($)

Sep. 30, 2014

Dec. 31, 2013

Fair Value Measurements [Abstract]

$ 0

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Interest rate on convertible debt (in hundredths)

$ 47,426,000

$ 52,096,000

2.75%

2 3/4 percent convertible senior notes [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Interest rate on convertible debt (in hundredths)

2.75%

Fair value of convertible notes

$ 490,000,000

Recurring basis [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

44,551,000

$ 133,233,000

47,426,000

52,096,000

Recurring basis [Member] | Corporate debt securities [Member]

626,627,000

696,517,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Debt securities issued by U.S. government agencies [Member]

^[1]

353,848,000

407,897,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Debt securities issued by the U.S. Treasury [Member]

106,397,000

^[1]

64,432,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Debt securities issued by states of the United States and political subdivisions of the states [Member]

9,040,000

15,328,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Equity securities [Member]

64,344,000

^[1]

22,255,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member]

^[2]

1,021,000

1,276,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

44,551,000

133,233,000

47,426,000

52,096,000

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Corporate debt securities [Member]

102,038,000

201,933,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt securities issued by U.S. government agencies [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt securities issued by the U.S. Treasury [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt securities issued by states of the United States and political subdivisions of the states [Member]

9,040,000

15,328,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Equity securities [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member]

^[2]

1,021,000

1,276,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member]

524,589,000

494,584,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt securities issued by U.S. government agencies [Member]

^[1]

353,848,000

407,897,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt securities issued by the U.S. Treasury [Member]

106,397,000

^[1]

64,432,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt securities issued by states of the United States and political subdivisions of the states [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity securities [Member]

64,344,000

^[1]

22,255,000

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member]

^[2]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate debt securities [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt securities issued by U.S. government agencies [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt securities issued by the U.S. Treasury [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt securities issued by states of the United States and political subdivisions of the states [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Recurring basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity securities [Member]

^[1]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]