Financial Commitments (Reconciliation of Outstanding Debt Balance to Reported Debt Balance) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 15, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total debt	$ 967,984		$ 1,025,465
Term Loan B
Debt Instrument [Line Items]
Outstanding Debt	420,750		423,938
Unamortized Discounts and Issuance Costs	(13,915)		(15,480)
Total debt	406,835		408,458
Convertible Notes
Debt Instrument [Line Items]
Outstanding Debt		$ 69,900	69,918
Unamortized Discounts and Issuance Costs			(2,040)
Total debt	0		67,878
2017 Senior Notes | Senior Notes
Debt Instrument [Line Items]
Outstanding Debt	500,000		500,000
Unamortized Discounts and Issuance Costs	(4,006)		(4,729)
Total debt	$ 495,994		$ 495,271