CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Comprehensive income:
Net income	$ 98.0	$ 79.4	$ 69.1
Derivative instruments:
Reclassification of losses to net income, net of tax of $0 and $0, and $0, respectively.	0.1	0.0	0.1
Other comprehensive income	0.1	0.0	0.1
Comprehensive income	$ 98.1	$ 79.4	$ 69.2