Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 80.2	$ 110.6
Available-for-sale securities:
Unrealized (loss) gain on available-for-sale securities, net of tax provisions of ($3.8) and ($22.1), respectively	(0.8)	38.1
Reclassification adjustment for realized net gains on available-for-sale securities included in net income, net of tax provision of zero and $60.3, respectively	(0.2)	(103.5)
Net change on available-for-sale securities, net of taxes	(1.0)	(65.4)
Cash flow hedges:
Unrealized (losses) gains on cash flow hedges, net of tax provisions of ($0.3) and ($0.6), respectively	(6.4)	2.1
Reclassification adjustment for realized net losses (gains) on cash flow hedges included in net income, net of tax provision (benefit) of $0.1 and ($0.1), respectively	3.1	(1.1)
Net change on cash flow hedges, net of taxes	(3.3)	1.0
Change in foreign currency translation adjustments	(11.1)	1.7
Other comprehensive loss, net of tax	(15.4)	(62.7)
Comprehensive income	$ 64.8	$ 47.9