Derivatives - Derivative Liabilities and Collateral Pledged (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Gross amounts of recognized liabilities	$ 67,480	$ 133,713
Derivative liabilities not subject to master netting agreements	43,000	61,900
Derivatives, interest rate contracts
Derivative [Line Items]
Gross amounts of recognized liabilities	24,431	71,853
Gross amounts offset in the Statements of Condition	0	0
Net amounts of liabilities presented in the Statements of Condition	24,431	71,853
Gross amounts not offset in the Statements of Condition, Derivative assets available for offset	(5,604)	(12,745)
Collateral pledged	(18,689)	(54,773)
Net amount	$ 138	$ 4,335