Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Doubtful Accounts
Changes in valuation allowances and reserves
Balance at beginning of year	$ 0.6	$ 0.3	$ 0.3
Charged to expense/(recovery)	0.1	0.3	1.4
Deductions and other	0.1		(1.4)
Balance at end of year	0.8	0.6	0.3
Valuation Allowance for Deferred Tax Assets
Changes in valuation allowances and reserves
Balance at beginning of year	44.7	48.8	54.9
Charged to expense/(recovery)	(39.5)	(4.1)	(3.2)
Deductions and other	1.7	(0.0)	(2.9)
Balance at end of year	$ 6.9	$ 44.7	$ 48.8