Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 108.8	$ 91.4
Available-for-sale securities:
Unrealized gains net of tax provision of $0.7 and benefit of $0.1, respectively	1.5	4.3
Reclassification adjustment for realized net (gains) losses included in net income, net of tax provisions of zero for each period	(0.1)	0.1
Net change on available-for-sale securities, net of taxes	1.4	4.4
Cash flow hedges:
Unrealized gains net of tax provision of $1.7 and $0.5, respectively	5.3	2.5
Reclassification adjustment for realized net losses included in net income, net of tax provision of $0.3 and benefit of $0.2, respectively	1.1	1.1
Net change on cash flow hedges, net of taxes	6.4	3.6
Change in foreign currency translation adjustments	7.9	3.7
Other comprehensive income, net of tax	15.7	11.7
Comprehensive income	$ 124.5	$ 103.1