Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in other current assets	$ 12,916		$ 11,829
Minimum protective endowment held in an interest-bearing account	500		500
Restricted cash
Cash and cash equivalents	262,941	$ 268,918	261,585
Restricted cash included in other current assets	12,916		11,829
Restricted cash included in other assets	500		500
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	276,357	279,212	$ 273,914	$ 202,020
United States
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in other current assets	900	700
Restricted cash
Restricted cash included in other current assets	900	700
Australia and New Zealand
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in other current assets	12,100	9,100
Restricted cash
Restricted cash included in other current assets	12,100	$ 9,100
PENNSYLVANIA
Restricted Cash and Cash Equivalents Items [Line Items]
Minimum protective endowment held in an interest-bearing account	500
Restricted cash
Restricted cash included in other assets	$ 500