Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 31.1	$ 34.4
Available-for-sale debt securities:
Change in net unrealized gains and losses, net of tax (provision) benefit of ($0.6) and $1.4, respectively	1.8	(2.0)
Net realized losses reclassified into net income, net of tax provisions of zero and zero, respectively	0.0	0.9
Net change on available-for-sale debt securities, net of tax	1.8	(1.1)
Cash flow hedges:
Change in net unrealized gains and losses, net of tax provision of $1.3 and $0.3, respectively	2.1	13.1
Net realized (gains) losses reclassified into net income, net of tax provisions of $0.2 and $0.6, respectively	1.2	(5.1)
Net change on cash flow hedges, net of tax	3.3	8.0
Change in foreign currency translation adjustments	2.2	5.3
Other comprehensive income, net of tax	7.3	12.2
Comprehensive income	$ 38.4	$ 46.6