Summary of Significant Accounting Policies - Revenue from Contracts with Customers (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) contract	Sep. 30, 2018 USD ($) contract
Summary of Significant Accounting Policies
Number of active contracts | contract			729,000	806,000
Transferred at Point in Time
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 26,600	$ 24,500	$ 76,300	$ 85,200
Transferred over Time
Summary of Significant Accounting Policies
Revenue from contract with customers	4,500	4,700	14,500	14,500
Trust and investment services income
Summary of Significant Accounting Policies
Revenue from contract with customers	7,320	7,527	22,309	22,608
Deposit account services
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 19,900	$ 18,000	$ 57,000	$ 63,700