Valuation Fair Value, Other Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due from brokers		$ 41,068	$ 18,531
Reverse repurchase agreements	[1]	76,610	13,987
Repurchase agreements	[1]	1,225,905	1,323,080
Due to brokers		2,654	583
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash		20,482	10,237
Due from brokers		41,068	18,531
Reverse repurchase agreements		76,610	13,987
Repurchase agreements		1,225,905	1,323,080
Due to brokers		2,654	583
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash		20,482	10,237
Due from brokers		41,068	18,531
Reverse repurchase agreements		76,610	13,987
Repurchase agreements		1,225,905	1,323,080
Due to brokers		$ 2,654	$ 583

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