CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 178.6	$ 235.5
Other comprehensive income:
Foreign currency translation losses		0.4
Defined benefit pension plan:
Actuarial loss arising during period, net of tax	(0.1)
Amortization of actuarial gain and prior service cost included in net periodic pension cost, net of tax	0.1	0.2
Total defined benefit pension plan, net of tax		0.2
Unrealized gain on available-for-sale securities, net of tax	0.1
Other comprehensive income, net of tax	0.1	0.6
Comprehensive income	$ 178.7	$ 236.1