Supplemental Cash Flow Information - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash, Cash Equivalents and Restricted Cash [Line Items]
Cash and cash equivalents	$ 212,473	$ 200,218	$ 184,620	$ 530,670	$ 377,205	$ 164,798
Total cash, cash equivalents, and restricted cash reported in the statements of cash flows	214,715	202,615	186,808	532,853	381,638	169,745
Prepaid Expenses and Other Current Assets
Cash, Cash Equivalents and Restricted Cash [Line Items]
Restricted cash and cash equivalents	1,460	1,518	1,275	1,266	3,514	4,026
Other Assets
Cash, Cash Equivalents and Restricted Cash [Line Items]
Restricted cash and cash equivalents	$ 782	$ 879	$ 913	$ 917	$ 919	$ 921