Summary of Significant Accounting Policies - Revenue from Contracts with Customers (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) contract	Mar. 31, 2019 USD ($)
Summary of Significant Accounting Policies
Number of active contracts | contract	735,000
Transferred at Point in Time
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 24,900	$ 24,100
Transferred over Time
Summary of Significant Accounting Policies
Revenue from contract with customers	4,600	5,000
Trust and investment services income
Summary of Significant Accounting Policies
Revenue from contract with customers	7,389	7,269
Deposit account services
Summary of Significant Accounting Policies
Revenue from contract with customers	$ 18,400	$ 18,100