Summary of Significant Accounting Policies - Revenue from Contracts with Customers (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) contract	Jun. 30, 2018 USD ($) contract
Summary of Significant Accounting Policies
Number of active contracts | contract			779,000	803,000
Transferred at Point in Time
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 25,600	$ 29,900	$ 49,700	$ 60,700
Transferred over Time
Summary of Significant Accounting Policies
Revenue from contract with customers	5,000	4,900	10,000	9,800
Trust and investment services income
Summary of Significant Accounting Policies
Revenue from contract with customers	7,720	7,567	14,989	15,081
Deposit account services
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 19,000	$ 22,900	$ 37,000	$ 45,700