Components of Statement of Income of the CFE (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collateralized Securities Transactions [Line Items]
Interest income										$ 313,039	$ 355,754	$ 452,268
Interest expense		$ (19,126)	$ (21,248)	$ (23,750)	$ (27,314)	$ (26,966)	$ (31,950)	$ (35,128)	$ (38,451)	(91,438)	(132,495)	(197,709)
Net interest margin		56,132	51,740	53,926	59,803	61,095	49,349	54,677	58,138	221,601	223,259	254,559
Gain on mortgage loans										(1,065)	8
Operating expenses		(18,135)	(11,543)	(8,957)	(8,250)	(9,073)	(7,125)	(7,310)	(7,161)
Net income		$ 145,491	$ (83,892)	$ 24,556	$ (34,535)	$ (25,851)	$ 77,891	$ (12,477)	$ 16,798	$ 51,620	$ 56,361	$ (134,136)
CFE
Collateralized Securities Transactions [Line Items]
Interest income	$ 446
Interest expense	(97)
Net interest margin	349
Gain on mortgage loans	3,571
Operating expenses	(8)
Net income	$ 3,912