Consolidated Statement of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Beginning Balance at Dec. 31, 2009	$ 1,013,941	$ 179,333	$ 693	$ 1,017,185	$ (356,154)	$ 172,884
Net income	126,896				126,896
Change in unrealized gain on mortgage securities, net	1,057					1,057
Amounts related to cash flow hedges, net	(41)					(41)
Cash dividends:
Common	(105,938)			(546)	(105,392)
Preferred	(20,233)				(20,233)
Conversion of preferred stock		(10)		10
Additions to capital	11,743		10	11,733
Ending Balance at Dec. 31, 2010	1,027,425	179,323	703	1,028,382	(354,883)	173,900
Net income	160,204				160,204
Change in unrealized gain on mortgage securities, net	54,325					54,325
Amounts related to cash flow hedges, net	(23,685)					(23,685)
Cash dividends:
Common	(145,242)			(5,407)	(139,835)
Preferred	(20,369)				(20,369)
Conversion of preferred stock		(15)		15
Additions to capital	240,049	5,206	180	234,663
Ending Balance at Dec. 31, 2011	1,292,707	184,514	883	1,257,653	(354,883)	204,540
Net income	163,626				163,626
Change in unrealized gain on mortgage securities, net	91,750					91,750
Amounts related to cash flow hedges, net	(2,380)					(2,380)
Cash dividends:
Common	(143,445)			(1,785)	(141,660)
Preferred	(21,021)				(21,021)
Conversion of preferred stock		(1)		1
Additions to capital	150,950	4,479	109	146,362
Common share repurchases	(35,062)		(30)	(35,032)
Ending Balance at Dec. 31, 2012	$ 1,497,125	$ 188,992	$ 962	$ 1,367,199	$ (353,938)	$ 293,910