Equity - AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated other comprehensive income [Line Items]
Balance at beginning of period			$ 16.6
Net current period other comprehensive income (loss)	$ 16.3	$ 20.6	(24.3)	$ (24.8)
Other Comprehensive Income (Loss), Net of Tax	16.3	$ 20.6	(24.3)	$ (24.8)
Balance at end of the period	(7.7)		(7.7)
Unrealized Gain on Available-for-Sale Securities
Accumulated other comprehensive income [Line Items]
Balance at beginning of period			94.1
Other Comprehensive Income (Loss), Net of Tax			(93.6)
Balance at end of the period	0.5		0.5
Unrealized Loss on Cash Flow Hedges
Accumulated other comprehensive income [Line Items]
Balance at beginning of period			(0.1)
Other Comprehensive Income (Loss), Net of Tax			0.2
Balance at end of the period	0.1		0.1
Foreign Currency Translation Adjustments
Accumulated other comprehensive income [Line Items]
Balance at beginning of period			(77.4)
Other Comprehensive Income (Loss), Net of Tax			69.1
Balance at end of the period	$ (8.3)		$ (8.3)