Schedule of Reverse Repurchase Agreements by Maturity (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2015
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements	[1]	$ 1,070,105	$ 1,174,189
Debt, Weighted Average Interest Rate		1.18%	0.97%
Remaining Days to Maturity, Reverse Repurchase Agreements		78 days	100 days
Agency residential mortgage-backed securities [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 815,774	$ 933,320
Debt, Weighted Average Interest Rate		0.70%	0.58%
Remaining Days to Maturity, Reverse Repurchase Agreements		39 days	56 days
Agency residential mortgage-backed securities [Member] | Maturity up to 30 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 361,738	$ 295,277
Debt, Weighted Average Interest Rate		0.69%	0.54%
Remaining Days to Maturity, Reverse Repurchase Agreements		15 days	14 days
Agency residential mortgage-backed securities [Member] | Maturity 31 to 60 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 254,400	$ 203,144
Debt, Weighted Average Interest Rate		0.69%	0.54%
Remaining Days to Maturity, Reverse Repurchase Agreements		43 days	44 days
Agency residential mortgage-backed securities [Member] | Maturity 61 to 90 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 199,636	$ 239,431
Debt, Weighted Average Interest Rate		0.72%	0.68%
Remaining Days to Maturity, Reverse Repurchase Agreements		78 days	74 days
Agency residential mortgage-backed securities [Member] | Maturity 91 to 120 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 0	$ 193,962
Debt, Weighted Average Interest Rate		0.00%	0.56%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	106 days
Agency residential mortgage-backed securities [Member] | Maturity 151 to 180 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 0	$ 1,506
Debt, Weighted Average Interest Rate		0.00%	1.57%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	175 days
Credit Portfolio [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 254,188	$ 240,869
Debt, Weighted Average Interest Rate		2.72%	2.47%
Remaining Days to Maturity, Reverse Repurchase Agreements		204 days	272 days
Credit Portfolio [Member] | Maturity up to 30 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 19,109	$ 14,674
Debt, Weighted Average Interest Rate		1.26%	1.94%
Remaining Days to Maturity, Reverse Repurchase Agreements		4 days	17 days
Credit Portfolio [Member] | Maturity 31 to 60 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 18,186	$ 26,419
Debt, Weighted Average Interest Rate		1.90%	1.87%
Remaining Days to Maturity, Reverse Repurchase Agreements		49 days	39 days
Credit Portfolio [Member] | Maturity 61 to 90 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 72,843	$ 82,292
Debt, Weighted Average Interest Rate		2.77%	2.46%
Remaining Days to Maturity, Reverse Repurchase Agreements		68 days	67 days
Credit Portfolio [Member] | Maturity 91 to 120 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 4,518	$ 0
Debt, Weighted Average Interest Rate		2.27%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		98 days	0 days
Credit Portfolio [Member] | Maturity 121 to 150 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 9,669	$ 0
Debt, Weighted Average Interest Rate		2.60%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		126 days	0 days
Credit Portfolio [Member] | Maturity 151 to 180 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 12,021	$ 24,193
Debt, Weighted Average Interest Rate		2.92%	2.62%
Remaining Days to Maturity, Reverse Repurchase Agreements		167 days	164 days
Credit Portfolio [Member] | Maturity 181 to 360 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 85,671	$ 23,877
Debt, Weighted Average Interest Rate		3.10%	2.80%
Remaining Days to Maturity, Reverse Repurchase Agreements		307 days	346 days
Credit Portfolio [Member] | Maturity greater than 360 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 32,171	$ 69,414
Debt, Weighted Average Interest Rate		2.72%	2.51%
Remaining Days to Maturity, Reverse Repurchase Agreements		484 days	666 days
US Treasury Securities [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 143	$ 0
Debt, Weighted Average Interest Rate		0.80%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		1 day	0 days
US Treasury Securities [Member] | Maturity up to 30 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 143	$ 0
Debt, Weighted Average Interest Rate		0.80%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		1 day	0 days

[1] In the Company's Consolidated Statement of Assets, Liabilities, and Equity, all balances associated with repurchase agreements, reverse repurchase agreements, and financial derivatives are presented on a gross basis.