Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 217.6	$ 166.5	$ 431.2	$ 328.2
Other comprehensive income/(loss), net of tax (Note 10):
Unrealized gains/(losses) on investment securities	0.8	5.2	(7.9)	9.6
Unrealized gains/(losses) on hedging activities	37.4	(41.2)	34.3	(58.2)
Foreign currency translation adjustments	(12.5)	(1.4)	(19.5)	(1.6)
Defined benefit pension plan adjustments	2.3	1.8	4.4	3.6
Total other comprehensive income/(loss)	28.0	(35.6)	11.3	(46.6)
Comprehensive income	$ 245.6	$ 130.9	$ 442.5	$ 281.6