Schedule of Reverse Repurchase Agreements by Maturity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	$ 1,669,433	[1]	$ 1,236,166	[1]
Debt, Weighted Average Interest Rate	0.65%		0.90%
Remaining Days to Maturity, Reverse Repurchase Agreements	105 days		56 days
Maturity up to 30 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	715,194		369,861
Debt, Weighted Average Interest Rate	0.22%		0.53%
Remaining Days to Maturity, Reverse Repurchase Agreements	14 days		14 days
Maturity 31 to 60 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	322,874		402,206
Debt, Weighted Average Interest Rate	0.52%		1.12%
Remaining Days to Maturity, Reverse Repurchase Agreements	44 days		45 days
Maturity 61 to 90 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	289,276		320,161
Debt, Weighted Average Interest Rate	0.52%		0.78%
Remaining Days to Maturity, Reverse Repurchase Agreements	71 days		72 days
Maturity 91 to 120 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	0		8,233
Debt, Weighted Average Interest Rate	0.00%		1.40%
Remaining Days to Maturity, Reverse Repurchase Agreements	0 days		100 days
Maturity 121 to 150 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	21,236		38,856
Debt, Weighted Average Interest Rate	2.03%		0.49%
Remaining Days to Maturity, Reverse Repurchase Agreements	139 days		135 days
Maturity 151 to 180 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	123,484		96,849
Debt, Weighted Average Interest Rate	1.25%		1.90%
Remaining Days to Maturity, Reverse Repurchase Agreements	162 days		179 days
Maturity 181 to 360 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	47,768		0
Debt, Weighted Average Interest Rate	0.85%		0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements	274 days		0 days
Maturity greater than 360 days [Member]
Reverse Repurchase Agreements [Line Items]
Reverse repurchase agreements	$ 149,601		$ 0
Debt, Weighted Average Interest Rate	2.41%		0.00%
Remaining Days to Maturity, Reverse Repurchase Agreements	631 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.