Debt - Schedule of long-term debt outstanding (Details) - USD ($)	Sep. 30, 2021	Jun. 30, 2021	Mar. 26, 2021	Jul. 10, 2020
Debt Instrument [Line Items]
Total	$ 694,800,000	$ 694,500,000
Less: amounts due within one year	0	0
Long-term debt, net of current portion	$ 694,800,000	$ 694,500,000
Senior unsecured notes, 4.45% due March 2023
Debt Instrument [Line Items]
Interest rate	4.45%	4.45%	4.45%
Face amount	$ 300,000,000	$ 300,000,000
Total	$ 299,600,000	$ 299,500,000	$ 300,000,000
Senior unsecured notes, 6.375% due July 2028
Debt Instrument [Line Items]
Interest rate	6.375%	6.375%		6.375%
Face amount	$ 400,000,000	$ 400,000,000		$ 400,000,000
Total	$ 395,200,000	$ 395,000,000.0