Consolidated Statements Of Equity (USD $) In Thousands, except Share data	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Total
Balance at Dec. 31, 2011	$ 5	$ 1,985	$ 1,239,180	$ (608,769)	$ (8,647)	$ 623,754	$ 623,754
Balance (in Shares) at Dec. 31, 2011	450,829	198,563,273
Net income				531,421		531,421	531,421
Change in fair value of interest rate swaps, net of tax					6,419	6,419	6,419
Total comprehensive income						537,840	537,840
Stock issuances under employee plans, including income tax benefits		52	15,172			15,224	15,224
Stock issuances under employee plans, including income tax benefits (in Shares)		5,224,948
Issuance of common stock in connection with equity offering, net of issuance costs		134	71,713			71,847	71,847
Issuance of common stock in connection with equity offering, net of issuance costs (in Shares)		13,377,171
Common stock returned under share lending facility		(39)	39
Common stock returned under share lending facility (in Shares)		(3,919,904)
Amortization of stock-based compensation			7,151			7,151	7,151
Balance at Dec. 31, 2012	5	2,132	1,333,255	(77,348)	(2,228)	1,255,816	1,255,816
Balance (in Shares) at Dec. 31, 2012	450,829	213,245,488
Net income				188,715		188,715	188,715	[1]
Change in fair value of interest rate swaps, net of tax					2,228	2,228	2,228
Total comprehensive income						190,943	190,943
Stock issuances under employee plans, including income tax benefits		44	13,492			13,536	13,536
Stock issuances under employee plans, including income tax benefits (in Shares)		4,372,689
Issuance of common stock in connection with preferred stock conversion, net of issuance costs	(2)	600	(948)			(350)	(350)
Issuance of common stock in connection with preferred stock conversion, net of issuance costs (in Shares)	(183,000)	60,000,000
Amortization of stock-based compensation			9,015			9,015	9,015
Balance at Dec. 31, 2013	3	2,776	1,354,814	111,367		1,468,960	1,468,960
Balance (in Shares) at Dec. 31, 2013	267,829	277,618,177
Net income				215,865		215,865	215,865	[1]
Total comprehensive income							215,865
Stock issuances under employee plans, including income tax benefits		25	20,150			20,175	20,175
Stock issuances under employee plans, including income tax benefits (in Shares)		2,563,012
Repurchase and retirement of common stock, net of expenses		(50)	(36,731)			(36,781)	(36,781)
Repurchase and retirement of common stock, net of expenses (in Shares)		(5,040,000)
Amortization of stock-based compensation			8,469			8,469	8,469
Balance at Dec. 31, 2014	$ 3	$ 2,751	$ 1,346,702	$ 327,232		$ 1,676,688	$ 1,676,688
Balance (in Shares) at Dec. 31, 2014	267,829	275,141,189

[1] Per share amounts do not add across due to rounding differences in quarterly amounts and due to the impact of differences between the quarterly and annual weighted average share calculations.