Fair Value of Financial Instruments - Valuation for Level 3 Liabilities (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
		Feb. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period			$ 8,048,053	$ 7,871,020	$ 5,319,573
Total gains (realized/unrealized)
Included in earnings	[1]		(133,245)	260,872	(521,416)
Purchases/(Sales)	[2]		(1,009,942)	0	3,146,676
Paydowns			(85,965)	(83,839)	(73,813)
Balance at the end of period			$ 6,818,901	$ 8,048,053	$ 7,871,020
PO Security
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Proceeds from sale of investments		$ 44,300
Gain on sale of investments		1,500
Multi-Family Collateralized Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deconsolidation of assets		1,100,000
Multi-family collateralized debt obligations, at fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deconsolidation of assets		$ 1,000,000

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

[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.