Valuation Fair Value, Other Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		$ 43,026	$ 40,166	$ 40,482	$ 45,237
Due from brokers		33,462	33,297
Reverse repurchase agreements	[1]	77,932	78,632
Repurchase agreements	[1]	1,158,962	1,222,719
Due to brokers		538	439
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents		43,026	40,166
Due from brokers		33,462	33,297
Reverse repurchase agreements		77,932	78,632
Repurchase agreements		1,158,962	1,222,719
Due to brokers		538	439
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		43,026	40,166
Due from brokers		33,462	33,297
Reverse repurchase agreements		77,932	78,632
Repurchase agreements		1,158,962	1,222,719
Due to brokers		$ 538	$ 439

[1] In the Company's Consolidated Balance Sheet, all balances associated with the repurchase agreements and financial derivatives are presented on a gross basis.