Property and Equipment, net - Depreciation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 188.2	$ 187.5	$ 571.8	$ 550.2