Stockholders' Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Components of Accumulated Other Comprehensive Income (Loss)
AOCI, beginning balance					$ 761,977
AOCI, ending balance	761,977				737,695		761,977
Reclassifications Out Of Accumulated Other Comprehensive Income (Loss) [Abstract]
Realized gain on sale of securities					19,833		7,493		7,500
OTTI recognized in earnings	0	0	280	920	0		1,200		10,570
Accumulated Other Comprehensive Income/(Loss)
Other-than-temporary impairments recognized in accumulated other comprehensive(loss)/income	2,600				609		2,600
Net Unrealized Gain/(Loss) on Available-for-Sale MBS
Components of Accumulated Other Comprehensive Income (Loss)
AOCI, beginning balance				55,491	824,808		55,491		393,822
OCI before reclassifications					(52,063)		778,010		(320,261)
Amounts reclassified from AOCI					(19,833)	[1]	(8,693)	[1]	(18,070)	[1]
Net OCI during the period					(71,896)	[2]	769,317	[2]	(338,331)	[2]
AOCI, ending balance	824,808				752,912		824,808		55,491
Reclassifications Out Of Accumulated Other Comprehensive Income (Loss) [Abstract]
Total reclassifications for period					19,833	[1]	8,693	[1]	18,070	[1]
Net Unrealized Gain/(Loss) on Available-for-Sale MBS | Reclassification out of Accumulated Other Comprehensive Income
Components of Accumulated Other Comprehensive Income (Loss)
Amounts reclassified from AOCI					19,833		8,693		18,070
Reclassifications Out Of Accumulated Other Comprehensive Income (Loss) [Abstract]
Realized gain on sale of securities					(19,833)		(7,493)		(7,500)
OTTI recognized in earnings					0		(1,200)		(10,570)
Total reclassifications for period					(19,833)		(8,693)		(18,070)
Net Unrealized Gain/(Loss) on Swaps
Components of Accumulated Other Comprehensive Income (Loss)
AOCI, beginning balance				(114,194)	(62,831)		(114,194)		(139,142)
OCI before reclassifications					47,614		51,363		24,948
Amounts reclassified from AOCI					0	[1]	0	[1]	0	[1]
Net OCI during the period					47,614	[2]	51,363	[2]	24,948	[2]
AOCI, ending balance	(62,831)				(15,217)		(62,831)		(114,194)
Reclassifications Out Of Accumulated Other Comprehensive Income (Loss) [Abstract]
Total reclassifications for period					0	[1]	0	[1]	0	[1]
Accumulated Other Comprehensive Income/(Loss):
Components of Accumulated Other Comprehensive Income (Loss)
AOCI, beginning balance				(58,703)	761,977		(58,703)		254,680
OCI before reclassifications					(4,449)		829,373		(295,313)
Amounts reclassified from AOCI					(19,833)	[1]	(8,693)	[1]	(18,070)	[1]
Net OCI during the period					(24,282)	[2]	820,680	[2]	(313,383)	[2]
AOCI, ending balance	761,977				737,695		761,977		(58,703)
Reclassifications Out Of Accumulated Other Comprehensive Income (Loss) [Abstract]
Total reclassifications for period					$ 19,833	[1]	$ 8,693	[1]	$ 18,070	[1]

[1] See separate table below for details about these reclassifications.

[2] For further information regarding changes in OCI, see the Company’s consolidated statement of comprehensive income/(loss).