Stockholders' Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)					$ 761,977
Other Comprehensive (Loss)/Income	(223,468)		(4,667)		(93,073)		264,887
Accumulated other comprehensive income/(loss)	668,904				668,904
Net Unrealized Gain on Available-for-Sale MBS
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	942,887		312,954		824,808		55,491
OCI before reclassifications	(238,762)		(17,227)		(119,383)		242,217
Amounts reclassified from AOCI	(3,254)	[1]	280	[1]	(4,554)	[1]	(1,701)	[1]
Other Comprehensive (Loss)/Income	(242,016)	[2]	(16,947)	[2]	(123,937)	[2]	240,516	[2]
Accumulated other comprehensive income/(loss)	700,871		296,007		700,871		296,007
Net Unrealized (Loss)/Gain on Swaps
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	(50,515)		(102,103)		(62,831)		(114,194)
OCI before reclassifications	18,548		12,280		30,864		24,371
Amounts reclassified from AOCI	0	[1]	0	[1]	0	[1]	0	[1]
Other Comprehensive (Loss)/Income	18,548	[2]	12,280	[2]	30,864	[2]	24,371	[2]
Accumulated other comprehensive income/(loss)	(31,967)		(89,823)		(31,967)		(89,823)
Total AOCI
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	892,372		210,851		761,977		(58,703)
OCI before reclassifications	(220,214)		(4,947)		(88,519)		266,588
Amounts reclassified from AOCI	(3,254)	[1]	280	[1]	(4,554)	[1]	(1,701)	[1]
Other Comprehensive (Loss)/Income	(223,468)	[2]	(4,667)	[2]	(93,073)	[2]	264,887	[2]
Accumulated other comprehensive income/(loss)	$ 668,904		$ 206,184		$ 668,904		$ 206,184

[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).