Fair Value of Financial Instruments - Valuation for Level 3 Assets (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ 7,213,641	$ 8,442,604
Total gains/(losses) (realized/unrealized)
Included in earnings	[1]	182,880	131,421
Included in other comprehensive income		63	68
Sales	[2]	0	(1,075,529)
Contributions		0	12,701
Paydowns		(34,745)	(19,793)
Distributions		(3,965)	(382)
Balance at the end of period		$ 7,357,874	$ 7,491,090

[1] Amounts included in interest income from multi-family loans held in securitization trusts, unrealized gain on multi-family loans and debt held in securitization trusts, realized gain (loss) on investment securities and related hedges and gain on deconsolidation.

[2] In February 2015, the Company sold a first loss PO security from one of the Company’s Consolidated K-Series securitizations obtaining total proceeds of approximately $44.3 million and realizing a gain of approximately $1.5 million. The sale resulted in a de-consolidation of $1.1 billion in Multi-Family loans held in a securitization trust and $1.0 billion in Multi-Family CDOs.