Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 27.8	$ 18.1
Other comprehensive income:
Amortization of net actuarial losses and prior service costs, net of income taxes of $1.8 million and $3.8 million	5.2	11.5
Comprehensive income	$ 33.0	$ 29.6