CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net (loss) income	$ (56.0)	$ 206.1	$ 122.6	$ 441.6
Other comprehensive income:
Foreign currency translation gains (losses)	0.2	(2.2)	0.2	(1.8)
Defined benefit pension plan:
Actuarial gain (loss) arising during period, net of tax		7.1	(0.1)	7.1
Amortization of actuarial gain and prior service cost included in net periodic pension cost, net of tax	0.2	0.2	0.3	0.4
Total defined benefit pension plan, net of tax	0.2	7.3	0.2	7.5
Unrealized loss on available-for-sale securities, net of tax	(0.3)		(0.2)
Other comprehensive income, net of tax	0.1	5.1	0.2	5.7
Comprehensive (loss) income	$ (55.9)	$ 211.2	$ 122.8	$ 447.3