Long‑Term Debt - Bank Credit Facility (Details)	Jan. 25, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 19, 2017 USD ($)
Debt Instrument [Line Items]
Total long-term debt		$ 1,302,845,000	$ 246,000,000
Credit Facility | Line of Credit
Debt Instrument [Line Items]
Remaining borrowing capacity		781,996,000	$ 253,850,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Accordion feature, increase limit	$ 200,000,000
Revolving Credit Facility | Credit Facility
Debt Instrument [Line Items]
Borrowings guaranteed through stock of foreign subsidiaries percentage	0.65
Revolving Credit Facility | Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 500,000
Revolving Credit Facility | New Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 850,000,000
Write off of unamortized debt issuance costs	353,000
Capitalization of professional fees	3,577,000
Debt covenant, cross-defaults of other debt threshold	50,000,000
Debt covenant, judgment defaults threshold	10,000,000
Letter of Credit | Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	50,000,000
Multi‑Currency Swing‑Line Sub‑Facility | Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 85,000,000
Letters of Credit And Surety Bonds | Credit Facility
Debt Instrument [Line Items]
Total long-term debt		$ 150,000
Revolving Credit Facility - Euro Currency | Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Revolving Credit Facility - Euro Currency | Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | Overnight Bank Funding Effective Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | Minimum
Debt Instrument [Line Items]
Unused capacity, commitment fee percentage	0.20%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.25%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | Maximum
Debt Instrument [Line Items]
Unused capacity, commitment fee percentage	0.30%
Revolving Credit Facility - Non-Euro Currency | Credit Facility | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%