Stock-Based Compensation Expense Related to Stock Options and Restricted Stock Units Accompanying Statement of Operation (Detail) (Stock Options And Restricted Stock Units, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share based compensation expense	$ 3,316	$ 1,020	$ 8,297	$ 2,959
Cost of revenue
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share based compensation expense	294	75	1,305	176
Sales and marketing expense
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share based compensation expense	1,118	355	2,244	825
Research and development expense
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share based compensation expense	258	133	598	613
General and administrative expense
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share based compensation expense	$ 1,646	$ 457	$ 4,150	$ 1,345