Debt - Borrowing Obligations (Details) - USD ($)	3 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Mar. 31, 2017	Mar. 13, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 07, 2015	Jun. 30, 2015
Debt Instrument [Line Items]
Deferred issuance costs related to our Revolving Credit Facility	$ (1,733,000)	$ (1,839,000)
Total debt	843,854,000	867,924,000
Less: current portion	(348,669,000)	(372,999,000)
Total long-term debt	495,185,000	494,925,000
Loss on extinguishment of debt	215,000			$ 0
5.625% Senior Notes due 2026
Debt Instrument [Line Items]
Senior Notes, net of deferred issuance costs	496,918,000	496,764,000					$ 500,000,000
Stated percentage							5.625%
Unamortized debt issuance expense	3,100,000	3,200,000
Effective percentage							5.625%
Convertible Debentures 1.0% Due 2035
Debt Instrument [Line Items]
Senior Notes, net of deferred issuance costs	$ 122,185,000	122,948,000
Stated percentage	1.00%							1.00%	1.00%
Unamortized debt issuance expense	$ 300,000	300,000
Unamortized discount	$ 5,500,000	7,000,000
Effective percentage	5.622%
Loss on extinguishment of debt	$ 0	2,100,000	$ 15,000,000
Convertible Debentures 1.25% Due 2025
Debt Instrument [Line Items]
Convertible Debentures, net of unamortized discount	$ 226,484,000	225,067,000
Stated percentage	1.25%				1.25%	1.25%
Unamortized debt issuance expense	$ 1,400,000	1,500,000
Unamortized discount	$ 33,600,000	36,100,000
Effective percentage	5.578%
Convertible Debentures 1.5% Due 2035
Debt Instrument [Line Items]
Convertible Debentures, net of unamortized discount	$ 0	24,984,000
Stated percentage										1.50%
Unamortized discount		$ 100,000
Effective percentage	5.394%