Unrecognized Tax Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Balance at beginning of period	$ 194.6	$ 161.0	$ 146.7
Increases as a result of tax positions taken during a prior year	8.3	28.2	5.3
Decreases as a result of tax positions taken during a prior year	(1.9)	(6.8)	(18.1)
Settlements with taxing authorities	(34.9)	(0.7)	(5.0)
Lapse of statutes of limitation	(10.6)	(1.1)	0
Increases as a result of tax positions taken during the current year	63.7	14.0	32.3
Balance at end of period	$ 219.2	$ 194.6	$ 161.0