Repurchase Agreements Repurchase Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 179,670	$ 176,913
U.S. Government agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	20,219	20,233
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	63,931	79,079
Collateralized Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	95,520	77,601
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	179,670	176,913
Maturity Overnight [Member] | U.S. Government agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	20,219	20,233
Maturity Overnight [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	63,931	79,079
Maturity Overnight [Member] | Collateralized Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 95,520	$ 77,601