Summary of Depreciation and Amortization of Property and Equipment Associated with Direct Costs of Network, Sales and Services and Other Depreciation Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Direct costs of network, sales and services									$ 36,040		$ 26,930		$ 22,134
Other depreciation and amortization									886		3,228		6,148
Subtotal									36,926		30,158		28,282
Amortization of acquired technologies	875	875	875	875	874	979	979	979	3,500	[1]	3,811	[1]	8,349	[1]
Total depreciation and amortization									$ 40,426		$ 33,969		$ 36,631

[1] Amortization of acquired technologies during the year ended December 31, 2009 included impairment charges of $4.1 million for acquired CDN advertising technology.