Schedule of Reverse Repurchase Agreements by Maturity (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Borrowings [Line Items]
Reverse repurchase agreements	[1]	$ 1,498,849	$ 1,209,315
Debt, Weighted Average Interest Rate		3.13%	1.98%
Remaining Days to Maturity, Reverse Repurchase Agreements		122 days	99 days
Agency residential mortgage-backed securities [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 917,262	$ 829,624
Debt, Weighted Average Interest Rate		2.59%	1.51%
Remaining Days to Maturity, Reverse Repurchase Agreements		47 days	44 days
Agency residential mortgage-backed securities [Member] | Maturity up to 30 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 245,956	$ 287,014
Debt, Weighted Average Interest Rate		2.46%	1.43%
Remaining Days to Maturity, Reverse Repurchase Agreements		17 days	15 days
Agency residential mortgage-backed securities [Member] | Maturity 31 to 60 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 415,379	$ 264,058
Debt, Weighted Average Interest Rate		2.58%	1.47%
Remaining Days to Maturity, Reverse Repurchase Agreements		46 days	46 days
Agency residential mortgage-backed securities [Member] | Maturity 61 to 90 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 255,421	$ 277,950
Debt, Weighted Average Interest Rate		2.74%	1.63%
Remaining Days to Maturity, Reverse Repurchase Agreements		76 days	74 days
Agency residential mortgage-backed securities [Member] | Maturity 91 to 120 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 506	$ 0
Debt, Weighted Average Interest Rate		3.31%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		91 days	0 days
Agency residential mortgage-backed securities [Member] | Maturity 121 to 150 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 0	$ 0
Debt, Weighted Average Interest Rate		0.00%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	0 days
Agency residential mortgage-backed securities [Member] | Maturity 151 to 180 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 0	$ 602
Debt, Weighted Average Interest Rate		0.00%	2.56%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	158 days
US Treasury Securities [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 273	$ 297
Debt, Weighted Average Interest Rate		3.10%	1.70%
Remaining Days to Maturity, Reverse Repurchase Agreements		2 days	2 days
US Treasury Securities [Member] | Maturity up to 30 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 273	$ 297
Debt, Weighted Average Interest Rate		3.10%	1.70%
Remaining Days to Maturity, Reverse Repurchase Agreements		2 days	2 days
Credit [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 581,314	$ 379,394
Debt, Weighted Average Interest Rate		3.98%	3.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		240 days	219 days
Credit [Member] | Maturity up to 30 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 30,426	$ 37,433
Debt, Weighted Average Interest Rate		2.55%	2.61%
Remaining Days to Maturity, Reverse Repurchase Agreements		22 days	13 days
Credit [Member] | Maturity 31 to 60 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 189,937	$ 132,201
Debt, Weighted Average Interest Rate		3.32%	2.44%
Remaining Days to Maturity, Reverse Repurchase Agreements		48 days	49 days
Credit [Member] | Maturity 61 to 90 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 93,202	$ 130,875
Debt, Weighted Average Interest Rate		3.21%	2.75%
Remaining Days to Maturity, Reverse Repurchase Agreements		74 days	77 days
Credit [Member] | Maturity 91 to 120 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 0	$ 0
Debt, Weighted Average Interest Rate		0.00%	0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements		0 days	0 days
Credit [Member] | Maturity 121 to 150 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 26,222	$ 8,551
Debt, Weighted Average Interest Rate		4.60%	3.79%
Remaining Days to Maturity, Reverse Repurchase Agreements		123 days	128 days
Credit [Member] | Maturity 151 to 180 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 9,491	$ 8,300
Debt, Weighted Average Interest Rate		4.64%	3.40%
Remaining Days to Maturity, Reverse Repurchase Agreements		166 days	164 days
Credit [Member] | Maturity 181 to 360 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 91,730	$ 5,090
Debt, Weighted Average Interest Rate		4.54%	3.59%
Remaining Days to Maturity, Reverse Repurchase Agreements		316 days	280 days
Credit [Member] | Maturity greater than 360 days [Member]
Borrowings [Line Items]
Reverse repurchase agreements		$ 140,306	$ 56,944
Debt, Weighted Average Interest Rate		5.15%	4.94%
Remaining Days to Maturity, Reverse Repurchase Agreements		636 days	1094 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.