Schedule of Reverse Repurchase Agreements by Maturity (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	[1]	$ 1,174,189	$ 1,669,433
Debt, Weighted Average Interest Rate		0.97%	0.65%
Remaining Days to Maturity, Reverse Repurchase Agreements		100 days	105 days
Agency residential mortgage-backed securities [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 933,320	$ 1,145,821
Debt, Weighted Average Interest Rate		0.58%	0.35%
Remaining Days to Maturity, Reverse Repurchase Agreements		56 days	50 days
Agency residential mortgage-backed securities [Member] | Maturity up to 30 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 295,277	$ 537,624
Debt, Weighted Average Interest Rate		0.54%	0.34%
Remaining Days to Maturity, Reverse Repurchase Agreements		14 days	16 days
Agency residential mortgage-backed securities [Member] | Maturity 31 to 60 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 203,144	$ 276,002
Debt, Weighted Average Interest Rate		0.54%	0.34%
Remaining Days to Maturity, Reverse Repurchase Agreements		44 days	44 days
Agency residential mortgage-backed securities [Member] | Maturity 61 to 90 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 239,431	$ 251,715
Debt, Weighted Average Interest Rate		0.68%	0.38%
Remaining Days to Maturity, Reverse Repurchase Agreements		74 days	72 days
Agency residential mortgage-backed securities [Member] | Maturity 91 to 120 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 193,962	$ 0
Debt, Weighted Average Interest Rate		0.56%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		106 days	0 days
Agency residential mortgage-backed securities [Member] | Maturity 151 to 180 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 1,506	$ 48,161
Debt, Weighted Average Interest Rate		1.57%	0.44%
Remaining Days to Maturity, Reverse Repurchase Agreements		175 days	164 days
Agency residential mortgage-backed securities [Member] | Maturity 181 to 360 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 0	$ 32,319
Debt, Weighted Average Interest Rate		0.00%	0.47%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	317 days
Credit Portfolio [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 240,869	$ 399,981
Debt, Weighted Average Interest Rate		2.47%	2.02%
Remaining Days to Maturity, Reverse Repurchase Agreements		272 days	295 days
Credit Portfolio [Member] | Maturity up to 30 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 14,674	$ 53,939
Debt, Weighted Average Interest Rate		1.94%	1.94%
Remaining Days to Maturity, Reverse Repurchase Agreements		17 days	22 days
Credit Portfolio [Member] | Maturity 31 to 60 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 26,419	$ 46,872
Debt, Weighted Average Interest Rate		1.87%	1.59%
Remaining Days to Maturity, Reverse Repurchase Agreements		39 days	43 days
Credit Portfolio [Member] | Maturity 61 to 90 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 82,292	$ 37,561
Debt, Weighted Average Interest Rate		2.46%	1.47%
Remaining Days to Maturity, Reverse Repurchase Agreements		67 days	65 days
Credit Portfolio [Member] | Maturity 121 to 150 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 0	$ 21,236
Debt, Weighted Average Interest Rate		0.00%	2.03%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	139 days
Credit Portfolio [Member] | Maturity 151 to 180 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 24,193	$ 75,323
Debt, Weighted Average Interest Rate		2.62%	1.77%
Remaining Days to Maturity, Reverse Repurchase Agreements		164 days	160 days
Credit Portfolio [Member] | Maturity 181 to 360 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 23,877	$ 15,449
Debt, Weighted Average Interest Rate		2.80%	1.65%
Remaining Days to Maturity, Reverse Repurchase Agreements		346 days	181 days
Credit Portfolio [Member] | Maturity greater than 360 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 69,414	$ 149,601
Debt, Weighted Average Interest Rate		2.51%	2.41%
Remaining Days to Maturity, Reverse Repurchase Agreements		666 days	631 days
US Treasury Securities [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 0	$ 123,631
Debt, Weighted Average Interest Rate		0.00%	(1.01%)
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	2 days
US Treasury Securities [Member] | Maturity up to 30 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements		$ 0	$ 123,631
Debt, Weighted Average Interest Rate		0.00%	(1.01%)
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	2 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.