Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Period in which short-term investment become cash equivalents	90 days
Cash and cash equivalents	$ 108,501	$ 89,817	$ 126,700
Restricted cash (included in other assets)	15,151	7,436	8,522
Total	$ 123,652	$ 97,253	$ 135,222	$ 13,181