Equity, Accumulated Other Comprehensive Income, Net of Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	$ 4,574.4
Other comprehensive gain (loss) before reclassifications	(15.8)	$ (14.5)
Amount reclassified from accumulated other comprehensive loss	(2.3)	9.1
Other comprehensive gain (loss), net	(18.1)	(5.4)
Balance at end of period	4,962.5	4,574.4
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	(19.2)	(13.8)
Balance at end of period	(37.3)	(19.2)
Unrealized Gains (Losses) on Available-for- Sale Securities [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	17.0	8.4
Other comprehensive gain (loss) before reclassifications	0.8	9.1
Amount reclassified from accumulated other comprehensive loss	(1.2)	(0.5)
Other comprehensive gain (loss), net	(0.4)	8.6
Balance at end of period	16.6	17.0
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	(1.3)	(4.2)
Other comprehensive gain (loss) before reclassifications	(2.1)	(6.7)
Amount reclassified from accumulated other comprehensive loss	(1.1)	9.6
Other comprehensive gain (loss), net	(3.2)	2.9
Balance at end of period	(4.5)	(1.3)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	(34.9)	(18.0)
Other comprehensive gain (loss) before reclassifications	(14.5)	(16.9)
Amount reclassified from accumulated other comprehensive loss	0.0	0.0
Other comprehensive gain (loss), net	(14.5)	(16.9)
Balance at end of period	$ (49.4)	$ (34.9)