Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Offsetting Liabilities [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ (12,800)	$ (13,200)
Securities Loaned [Member]
Offsetting Liabilities [Line Items]
Securities Loaned, Gross	9,518	33,645
Securities Loaned, Asset	0	0
Securities Loaned	9,518	33,645
Securities Loaned, Collateral, Right to Reclaim Securities	0	0
Securities Loaned, Collateral, Right to Reclaim Cash	(9,518)	(33,645)
Securities Loaned, Amount Offset Against Collateral	0	0
Derivatives [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	12,221	9,392
Derivative Liability, Fair Value, Gross Asset	0	0
Derivatives	12,221	9,392
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	(12,221)	(9,392)
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Exchange Traded [Member] | Short [Member] | Exchange Traded Options [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	843	7,118
Derivative Liability, Fair Value, Gross Asset	0	0
Derivatives	843	7,118
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 843	$ 7,118