Offsetting Assets and Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) counterparty	Dec. 31, 2015 USD ($)
Swaps, at fair value
Gross Amounts of Recognized Assets	$ 0	$ 1,127
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	0	1,127
Gross Amounts Not Offset in the Consolidated Balance Sheets
Financial Instruments	0	(1,127)
Cash Collateral Received	0	0
Net Amount	0	0
Swaps, at fair value
Gross Amounts of Recognized Liabilities	131,971	70,526
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	131,971	70,526
Gross Amounts Not Offset in the Consolidated Balance Sheets
Financial Instruments	0	0
Cash Collateral Pledged	(131,971)	(70,526)
Net Amount	0	0
Repurchase agreements and other advances
Gross Amounts of Recognized Liabilities	9,038,537	9,388,902
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	9,038,537	9,388,902
Gross Amounts Not Offset in the Consolidated Balance Sheets
Financial Instruments	(9,031,347)	(9,387,937)
Cash Collateral Pledged	(7,190)	(965)
Net Amount	0	0
Total
Gross Amounts of Recognized Liabilities	9,170,508	9,459,428
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	9,170,508	9,459,428
Gross Amounts Not Offset in the Consolidated Balance Sheet
Financial Instruments	(9,031,347)	(9,387,937)
Cash Collateral Pledged	(139,161)	(71,491)
Net Amount	0	0
Additional disclosures
Excess collateral	3,900	47
Fair value of securities pledged against the swaps	35,700	38,600
Fair value of financial instruments pledged against the repurchase agreements and other advances	10,900,000	11,300,000
Unamortized debt issuance expense	$ 450	1,280
Number of repurchase agreement counterparties with unconditional right of setoff | counterparty	1
Swaps, at fair value
Swaps, at fair value
Gross Amounts of Recognized Assets	$ 0	1,127
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	0	1,127
Gross Amounts Not Offset in the Consolidated Balance Sheets
Financial Instruments	0	(1,127)
Cash Collateral Received	0	0
Net Amount	$ 0	$ 0