Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI, Debt Securities, Available-for-sale, Adjustment, after Tax	$ (4.3)	$ (6.0)	$ (5.3)	$ (6.8)
Foreign currency translation adjustment:
Balance at beginning of period	(716.4)	(585.3)
Other comprehensive income before reclassifications	12.3	(92.2)
Amount reclassified from accumulated other comprehensive loss, net of tax	5.8	13.4
Balance at end of period	(698.3)	(664.1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	1.0	0.8
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments and Tax	0.0	0.0
Derivative instruments:
Balance at beginning of period	(219.4)	(235.7)
Other comprehensive income before reclassifications	1.5	(0.9)
Amount reclassified from accumulated other comprehensive loss, net of tax	2.6	3.3
Balance at end of period	(215.3)	(233.3)
Total:
Balance at beginning of period	(941.1)	(827.8)
Other comprehensive income before reclassifications	13.8	(93.1)
Amount reclassified from accumulated other comprehensive loss, net of tax	9.4	17.5
Balance at end of period	$ (917.9)	$ (903.4)