Consolidated Statement of Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2010	$ 770,767	$ 1,960,871	$ (4,179)	$ (1,185,925)
Shares, balance at Dec. 31, 2010		61,926,187
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Change in unrealized gain or loss on investments and MBS available for sale	65,294		65,294
Equity based compensation and related tax amounts	3,363	3,363
Equity based compensation, shares		131,458
Net Income	39,133			39,133
Balance at Dec. 31, 2011	878,557	1,964,234	61,115	(1,146,792)
Shares, balance at Dec. 31, 2011		62,057,645
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Change in unrealized gain or loss on investments and MBS available for sale	(403)		(403)
Equity based compensation and related tax amounts	3,130	3,130
Equity based compensation, shares		110,958
Employee stock purchase plan	661	661
Employee stock purchase plan, shares	38,926	38,926
Cash dividends paid to common shareholders	(49,743)			(49,743)
Net Income	385,721			385,721
Balance at Dec. 31, 2012	1,217,923	1,968,025	60,712	(810,814)
Shares, balance at Dec. 31, 2012	62,207,529	62,207,529
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Change in unrealized gain or loss on investments and MBS available for sale	(40,855)		(40,855)
Equity based compensation and related tax amounts	3,564	3,564
Equity based compensation, shares		120,024
Employee stock purchase plan	868	868
Employee stock purchase plan, shares	36,188	36,188
Cash dividends paid to common shareholders	(59,194)			(59,194)
Net Income	93,641			93,641
Balance at Dec. 31, 2013	$ 1,215,947	$ 1,972,457	$ 19,857	$ (776,367)
Shares, balance at Dec. 31, 2013	62,363,741	62,363,741