Equity - Accumulated Other Comprehensive Income (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at December 31, 2014	$ (28.2)
Unrealized (loss) gains, arising during the period	(98.8)
Amounts reclassified out of AOCI during the period	9.7
Taxes on unrealized gains (losses), arising during the period	17.6
Noncontrolling interest	63.3
Balance at September 30, 2015	(36.4)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at December 31, 2014	(42.4)
Unrealized (loss) gains, arising during the period	(118.4)
Amounts reclassified out of AOCI during the period	18.8
Taxes on unrealized gains (losses), arising during the period	30.4
Noncontrolling interest	55.6
Balance at September 30, 2015	(56.0)
Currency Derivative Contracts
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at December 31, 2014	14.4
Unrealized (loss) gains, arising during the period	19.5
Amounts reclassified out of AOCI during the period	(9.0)
Taxes on unrealized gains (losses), arising during the period	(12.8)
Noncontrolling interest	7.7
Balance at September 30, 2015	19.8
Marketable Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at December 31, 2014	(0.2)
Unrealized (loss) gains, arising during the period	0.1
Amounts reclassified out of AOCI during the period	(0.1)
Taxes on unrealized gains (losses), arising during the period	0.0
Noncontrolling interest	0.0
Balance at September 30, 2015	$ (0.2)