Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Trust Assets) (Details) $ in Thousands	Dec. 31, 2018 USD ($) trust_accounts	Dec. 31, 2017 USD ($) trust_accounts
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of Trust Accounts managed or administered | trust_accounts	1,141	1,119
Value of Trust Accounts | $	$ 1,129,600	$ 997,790