Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at beginning of period	$ 119.6	$ 111.0	$ 113.2
Additions for current year tax positions	17.4	5.2	3.4
Additions for prior year positions	31.9	3.4	13.8
Reductions for settlements with tax authorities	(46.1)	0	(19.4)
Reductions for expirations of statute of limitations	0	0	0
Balance at end of period	$ 122.8	$ 119.6	$ 111.0