Condensed Consolidated Statements of Changes in Common Stockholders' Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Parent	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings/(Deficit)	Accumulated Other Comprehensive Income (Loss)
Balance, at Dec. 31, 2012		$ 736,325	$ 151	$ (892,094)	$ 1,967,414	$ (355,241)	$ 16,095
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(187,500)	(187,500)				(187,500)
Net unrealized gain on investments, net of tax	7,445	7,445					7,445
Issuance of common stock - stock offering		299,542	39	0	299,503
Issuance of common stock under benefit plans		271			271
Issuance of common stock under incentive plans		62			62
Amortization of restricted stock		208			208
Issuance of convertible debt		77,026			77,026
Stock-based compensation expense, net		(1,999)			(1,999)
Dividends declared		(334)			(334)
Balance, at Mar. 31, 2013		931,046	190	(892,094)	2,342,151	(542,741)	23,540
Balance, at Dec. 31, 2013	939,645	939,645	191	(892,807)	2,347,104	(552,226)	37,383
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	202,759	202,759				202,759
Net unrealized gain on investments, net of tax	3,961	3,961					3,961
Repurchases of common stock under incentive plans		(130)		(130)	0
Issuance of common stock under benefit plans		458	0		458
Issuance of common stock under incentive plans		13			13
Amortization of restricted stock		459			459
Stock-based compensation expense, net		(149)			(149)
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature Whose Contractual Trigger Has Been Met		(91,016)			(91,016)
Dividends declared		(433)			(433)	0
Balance, at Mar. 31, 2014	$ 1,055,567	$ 1,055,567	$ 191	$ (892,937)	$ 2,256,436	$ (349,467)	$ 41,344