Amortization Expense of Acquired Intangibles (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Amortization expense:
Total amortization expense	$ 3,424	$ 2,773	$ 7,180	$ 5,550
Cost of revenue
Amortization expense:
Total amortization expense	1,444	1,541	3,284	3,082
Selling and marketing
Amortization expense:
Total amortization expense	1,499	1,232	2,995	2,464
General and administrative
Amortization expense:
Total amortization expense	$ 481		$ 901	$ 4