Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 5.9	$ 5.1
Other comprehensive income:
Amortization of actuarial losses and prior service credits, net of income taxes	9.7	9.1
Comprehensive income	$ 15.6	$ 14.2