Fair Value of Financial Instruments - Valuation for Level 3 Liabilities (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ 6,818,901	$ 8,048,053
Total gains/(losses) (realized/unrealized)
Included in earnings	[1]	221,899	(46,999)
Sales	[2]	0	(1,031,268)
Paydowns		(58,987)	(37,694)
Balance at the end of period		$ 6,981,813	$ 6,932,092

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

[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.