Balance Sheet Offsetting and Repurchase Agreements Accounted for as Secured Borrowings - Repurchase agreements accounted for as secured borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	$ 50,000	$ 100,000
Gross amount of recognized liabilities for repurchase agreements in offsetting disclosure	50,000	100,000
Amounts related to agreements not included in offsetting disclosure	0	0
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	0	0
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	0	0
30 to 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	50,000	100,000
91 to 110 days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	0	0
Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	50,000	100,000
Mortgage-backed securities | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	0	0
Mortgage-backed securities | Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	0	0
Mortgage-backed securities | 30 to 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	50,000	100,000
Mortgage-backed securities | 91 to 110 days
Assets Sold under Agreements to Repurchase [Line Items]
Remaining Contractual Maturity of the Agreements	$ 0	$ 0