Schedule of Reverse Repurchase Agreements by Maturity (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements	[1]	$ 1,033,581	$ 1,174,189
Debt, Weighted Average Interest Rate		1.32%	0.97%
Remaining Days to Maturity, Reverse Repurchase Agreements		56 days	100 days
Agency residential mortgage-backed securities [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 790,312	$ 933,320
Debt, Weighted Average Interest Rate		0.89%	0.58%
Remaining Days to Maturity, Reverse Repurchase Agreements		41 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		$ 405,725	$ 295,277
Debt, Weighted Average Interest Rate		0.83%	0.54%
Remaining Days to Maturity, Reverse Repurchase Agreements		18 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		$ 195,288	$ 203,144
Debt, Weighted Average Interest Rate		0.94%	0.54%
Remaining Days to Maturity, Reverse Repurchase Agreements		45 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		$ 149,965	$ 239,431
Debt, Weighted Average Interest Rate		0.97%	0.68%
Remaining Days to Maturity, Reverse Repurchase Agreements		74 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		$ 8,240	$ 193,962
Debt, Weighted Average Interest Rate		0.83%	0.56%
Remaining Days to Maturity, Reverse Repurchase Agreements		102 days	106 days
Agency residential mortgage-backed securities [Member] | Maturity 121 to 150 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 11,798	$ 0
Debt, Weighted Average Interest Rate		0.96%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		131 days	0 days
Agency residential mortgage-backed securities [Member] | Maturity 151 to 180 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 19,296	$ 1,506
Debt, Weighted Average Interest Rate		1.05%	1.57%
Remaining Days to Maturity, Reverse Repurchase Agreements		164 days	175 days
Credit Portfolio [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 237,841	$ 240,869
Debt, Weighted Average Interest Rate		2.75%	2.47%
Remaining Days to Maturity, Reverse Repurchase Agreements		105 days	272 days
Credit Portfolio [Member] | Maturity up to 30 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 94,849	$ 14,674
Debt, Weighted Average Interest Rate		2.55%	1.94%
Remaining Days to Maturity, Reverse Repurchase Agreements		16 days	17 days
Credit Portfolio [Member] | Maturity 31 to 60 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 26,974	$ 26,419
Debt, Weighted Average Interest Rate		2.36%	1.87%
Remaining Days to Maturity, Reverse Repurchase Agreements		47 days	39 days
Credit Portfolio [Member] | Maturity 61 to 90 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 41,522	$ 82,292
Debt, Weighted Average Interest Rate		2.43%	2.46%
Remaining Days to Maturity, Reverse Repurchase Agreements		77 days	67 days
Credit Portfolio [Member] | Maturity 91 to 120 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 10,084	$ 0
Debt, Weighted Average Interest Rate		2.91%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		97 days	0 days
Credit Portfolio [Member] | Maturity 121 to 150 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 1,239	$ 0
Debt, Weighted Average Interest Rate		2.73%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		124 days	0 days
Credit Portfolio [Member] | Maturity 151 to 180 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 12,616	$ 24,193
Debt, Weighted Average Interest Rate		3.17%	2.62%
Remaining Days to Maturity, Reverse Repurchase Agreements		165 days	164 days
Credit Portfolio [Member] | Maturity 181 to 360 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 50,557	$ 23,877
Debt, Weighted Average Interest Rate		3.46%	2.80%
Remaining Days to Maturity, Reverse Repurchase Agreements		316 days	346 days
Credit Portfolio [Member] | Maturity greater than 360 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 0	$ 69,414
Debt, Weighted Average Interest Rate		0.00%	2.51%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	666 days
US Treasury Securities [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 5,428	$ 0
Debt, Weighted Average Interest Rate		0.91%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		4 days	0 days
US Treasury Securities [Member] | Maturity up to 30 days [Member]
Repurchase Agreements and Securitized Debt [Line Items]
Reverse repurchase agreements		$ 5,428	$ 0
Debt, Weighted Average Interest Rate		0.91%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		4 days	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.