Income Taxes - Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes
Current income taxes (benefits): U.S. federal	$ 225.9	$ 242.1	$ 109.5
Current income taxes (benefits): State	12.3	4.7	7.7
Current income taxes (benefits): Foreign	32.6	67.6	69.7
Current income taxes (benefits): Tax benefit of operating loss carryforwards	(52.0)	(163.0)	(134.1)
Total current income taxes (benefits)	218.8	151.4	52.8
Deferred income taxes (benefits): U.S. federal	79.1	148.0	155.1
Deferred income taxes (benefits): State	(1.0)	(32.8)	(3.1)
Deferred income taxes (benefits): Foreign	(119.3)	51.9	(16.9)
Deferred income taxes (benefits)	(41.2)	167.1	135.1
Income taxes (benefits)	$ 177.6	$ 318.5	$ 187.9