Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits:
Balance at beginning of year	$ 251.8	$ 219.2
Increases related to prior year tax positions	0.0	2.8
Decreases related to prior year tax positions	0.0	0.0
Increases related to current year tax positions	84.8	44.4
Settlements	0.0	(10.0)
Lapse of statute	(10.8)	(4.6)
Balance at end of year	325.8	251.8
Unrecognized tax benefits that, if recognized, would have a net impact on the effective tax rate	300.8
Accrued interest related to uncertain tax positions	$ 32.6	$ 28.1