Transfers Accounted for as Secured Borrowings (Details) - U.S. Government-sponsored mortgage-backed securities - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	$ 146,480	$ 155,325
Remaining Contractual Maturity of the Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	129,617	131,537
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	1,337	5,680
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	10,253	8,892
Greater Than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	$ 5,273	$ 9,216