Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 31.7	$ 32.9	$ 102.3	$ 115.7
Other comprehensive income:
Amortization of net actuarial losses, net of income taxes of $3.3 million, $2.2 million, $10.0 million, and $6.8 million	10.1	6.9	30.3	20.9
Comprehensive income	$ 41.8	$ 39.8	$ 132.6	$ 136.6