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, 2013	$ 1,384,687us-gaap_StockholdersEquity	$ 70,535	$ 550,400	$ (631)	$ 46,196	$ 718,187
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(9,753)us-gaap_NetIncomeLoss					(9,753)
Other comprehensive income	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	1,654,949us-gaap_StockholdersEquity	72,390	542,003	(313)	332,435	708,434
Stockholders' equity at beginning of period at Dec. 31, 2014	2,139,876us-gaap_StockholdersEquity	76,062	513,218	0	721,401	829,195
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	5,903us-gaap_NetIncomeLoss					5,903
Other comprehensive income	172,337				172,337
Share-based compensation, including excess income tax benefits	4,515		4,515
Issuance of common stock under compensation plans, including excess income tax benefits	4,089	619	3,470
Stockholders' equity at end of period at Mar. 31, 2015	$ 2,326,720us-gaap_StockholdersEquity	$ 76,681	$ 521,203	$ 0	$ 893,738	$ 835,098

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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- Definition

Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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