Property and Equipment, Net (Detail) (USD $)	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 and amortization expense			$ 61,208,000	$ 44,651,000
Internal-Use Software [Member]
Property, Plant and Equipment [Line Items]
Capitalized stock-based compensation expense	100,000	100,000	300,000	100,000
Property and equipment, types [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 400,000	$ 100,000	$ 900,000	$ 300,000