Summary of Significant Accounting Policies - Adoption of New Accounting Standards (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies
Assets	$ 4,634,114	$ 4,109,463	$ 3,096,562
Liabilities	$ 4,056,225	$ 3,532,755