CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Comprehensive income:
Net income	$ 138.8	$ 133.7
Derivative instruments:
Reclassification of losses to net income, net of tax of $0.1, and $0.1, respectively	0.3	0.3
Other comprehensive income	0.3	0.3
Comprehensive income	$ 139.1	$ 134.0