Derivative Financial Instruments and Hedging Table of Derivatives subject to netting agreement (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative assets	$ 32,069	$ 36,669
Credit Default Swap, Selling Protection | Credit Default Swap
Derivative [Line Items]
Gross assets recognized	25,369	28,731
Credit Default Swap, Buying Protection | Credit Default Swap
Derivative [Line Items]
Gross assets recognized	10,786	14,501
Credit Index Product | Credit Default Swap
Derivative [Line Items]
Gross assets recognized	14,583	14,230
Cash collateral	(1,632)	(1,632)
Derivative assets	$ 12,951	$ 12,598