Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 91.4	$ 80.2
Available-for-sale securities:
Unrealized gain (loss) on available-for-sale securities, net of tax benefit (provision) of $0.1 and ($3.8), respectively	4.3	(0.8)
Reclassification adjustment for realized net loss (gain) on available-for-sale securities included in net income, net of tax provision of zero, respectively	0.1	(0.2)
Net change on available-for-sale securities, net of taxes	4.4	(1.0)
Cash flow hedges:
Unrealized gain (loss) on cash flow hedges, net of tax provisions of ($0.5) and ($0.3), respectively	2.5	(6.4)
Reclassification adjustment for realized net losses on cash flow hedges included in net income, net of tax (benefit) provision of ($0.2) and $0.1, respectively	1.1	3.1
Net change on cash flow hedges, net of taxes	3.6	(3.3)
Change in foreign currency translation adjustments	3.7	(11.1)
Other comprehensive income (loss), net of tax	11.7	(15.4)
Comprehensive income	$ 103.1	$ 64.8