Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 145.4	$ 99.3	$ 227.0	$ 176.6
Available-for-sale debt securities:
Change in net unrealized gains, net of tax benefit of $0.1and $2.0 during the three and nine months ended September 30, 2020, respectively, and tax provision of zero and $(0.8) for the comparable periods in 2019, respectively	0.5	0.0	6.2	3.8
Net realized gains and losses reclassified into net income, net of tax	(0.8)	(0.1)	(0.5)	(0.1)
Net change on available-for-sale debt securities, net of tax	(0.3)	(0.1)	5.7	3.7
Cash flow hedges:
Change in net unrealized gains and (losses), net of tax provision of $(5.5) and $(3.1) during the three and nine months ended September 30, 2020, respectively, and tax provision of $(0.2) and $(1.3) for the comparable periods in 2019, respectively	29.8	(12.6)	21.0	(12.3)
Net realized losses reclassified into net income, net of tax benefit of $0.4 and $1.3 during the three and nine months ended September 30, 2020, respectively, and tax provision of $(0.7) and $(1.5) for the comparable periods in 2019, respectively	1.0	1.5	8.5	3.0
Net change on cash flow hedges, net of tax	30.8	(11.1)	29.5	(9.3)
Change in foreign currency translation adjustments	7.6	(4.3)	(1.5)	(3.0)
Other comprehensive loss, net	38.1	(15.5)	33.7	(8.6)
Comprehensive income	$ 183.5	$ 83.8	$ 260.7	$ 168.0