Derivative Liabilities and Collateral Pledged (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Gross amounts of recognized liabilities	$ 83,146	$ 135,897
Derivative Liabilities not subject to master netting agreements	13,200	39,500
Subject to Master Netting Agreements | Derivatives, Interest Rate Contracts
Derivative [Line Items]
Gross amounts of recognized liabilities	69,988	96,363
Gross amounts offset in the Statement of Condition	0	0
Net amounts of liabilities presented in the Statement of Condition	69,988	96,363
Derivative assets available for offset	(23,283)	(25,953)
Collateral pledged	(42,686)	(60,746)
Net amount	$ 4,019	$ 9,664