Consolidated Statements of Changes in Common Stockholders' Equity (USD $) In Thousands	Total	Parent [Member]	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings/(Deficit)	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, at Dec. 31, 2011		$ 1,182,291	$ 151	$ (892,052)	$ 1,966,565	$ 96,227	$ 11,400
Net income (loss)	(451,468)	(451,468)				(451,468)	0
Net foreign currency translation adjustment, net of tax	(7)	(7)					(7)
Net unrealized gain on investments, net of tax	5,348	4,860					4,860
Repurchases of common stock under incentive plans		(42)		(42)	0
Issuance of common stock under benefit plans		489	0		489
Amortization of restricted stock		57			57
Net actuarial gain (loss)		(158)					(158)
Stock-based compensation expense, net		1,638			1,638
Dividends declared		(1,335)			(1,335)
Dividends, Common Stock						0
Balance, at Dec. 31, 2012		736,325	151	(892,094)	1,967,414	(355,241)	16,095
Net income (loss)	(196,985)	(196,985)				(196,985)
Net foreign currency translation adjustment, net of tax	0
Net unrealized gain on investments, net of tax	18,493	21,090					21,090
Repurchases of common stock under incentive plans		(713)		(713)	0
Issuance of common stock - stock offering		299,410	39		299,371
Issuance of common stock under incentive plans		63	1		62
Issuance of common stock under benefit plans	0	672	0		672
Issuance of convertible debt (See Note 11)		77,026			77,026
Amortization of restricted stock		21			21
Net actuarial gain (loss)		198					198
Stock-based compensation expense, net		4,170			4,170
Debt Instrument, Convertible, Gross Amount of Equity Component	0
Dividends declared		(1,632)			(1,632)
Dividends, Common Stock						0
Balance, at Dec. 31, 2013	939,645	939,645	191	(892,807)	2,347,104	(552,226)	37,383
Net income (loss)	959,517	959,517				959,517
Net foreign currency translation adjustment, net of tax	(226)	(226)					(226)
Net unrealized gain on investments, net of tax	14,689	14,387					14,387
Repurchases of common stock under incentive plans		(154)		(154)	0
Issuance of common stock - stock offering		247,188	18		247,170
Issuance of common stock under incentive plans		182	0	0	182
Issuance of common stock under benefit plans		959	0		959
Net actuarial gain (loss)		(59)	0	0	0	0	(59)
Stock-based compensation expense, net		12,176			12,176
Reclassification to equity component of currently redeemable convertible senior notes		(74,690)			(74,690)
Debt Instrument, Convertible, Gross Amount of Equity Component	74,690
Dividends declared		(1,865)			(1,388)
Dividends, Common Stock						(477)
Balance, at Dec. 31, 2014	$ 2,097,060	$ 2,097,060	$ 209	$ (892,961)	$ 2,531,513	$ 406,814	$ 51,485