Debt - Schedule of long-term debt outstanding (Details) - USD ($)	Dec. 31, 2020	Jul. 10, 2020	Jun. 30, 2020
Debt Instrument [Line Items]
Total	$ 694,000,000.0		$ 551,800,000
Less: amounts due within one year	0		0
Long-term debt, net of current portion	694,000,000.0		$ 551,800,000
Senior unsecured notes, 5.20% due July 2021
Debt Instrument [Line Items]
Interest rate			5.20%
Face amount		$ 250,000,000.0	$ 250,000,000.0
Total	$ 0		$ 252,300,000
Senior unsecured notes, 4.45% due March 2023
Debt Instrument [Line Items]
Interest rate	4.45%		4.45%
Face amount	$ 300,000,000.0		$ 300,000,000.0
Total	$ 299,300,000		299,500,000
Senior unsecured notes, 6.375% due July 2028
Debt Instrument [Line Items]
Interest rate	6.375%
Face amount	$ 400,000,000.0	$ 400,000,000
Total	$ 394,700,000		$ 0