Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Unallocated Common Stock Held By ESOP [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]
Stockholders' equity at beginning of period at Dec. 31, 2012	$ 1,720,237	$ 61,751	$ 496,715	$ (2,583)	$ 686,807	$ 477,547
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	26,031					26,031
Other comprehensive income (loss)	(25,144)				(25,144)
Allocation of common stock by ESOP, including excess income tax benefits	375		58	317
Share-based compensation, including excess income tax benefits	1,488		1,488
Issuance of common stock under compensation plans, including excess income tax benefits	7,242	1,033	6,209
Stockholders' equity at end of period at Mar. 31, 2013	1,730,229	62,784	504,470	(2,266)	661,663	503,578
Stockholders' equity at beginning of period at Dec. 31, 2013	1,384,687	70,535	550,400	(631)	46,196	718,187
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(9,753)					(9,753)
Other comprehensive income (loss)	286,239				286,239
Allocation of common stock by ESOP, including excess income tax benefits	682		364	318
Share-based compensation, including excess income tax benefits	2,578		2,578
Issuance of common stock under compensation plans, including excess income tax benefits	6,639	908	5,731
Extinguishment of convertible senior notes, net of tax, including shares of common stock issued upon conversion	(16,123)	947	(17,070)
Stockholders' equity at end of period at Mar. 31, 2014	$ 1,654,949	$ 72,390	$ 542,003	$ (313)	$ 332,435	$ 708,434