Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Accruals and reserves, net	$ 24,548	$ 26,086
Allowance for doubtful accounts	12,194	14,159
Stock-based compensation, net	12,086	10,773
Deferred revenue	13,294	17,422
Net operating loss carryforwards	78,909	90,463
Research and development tax credit	26,863	24,313
AMT credits	6,070	5,606
Other	7,012	3,617
Less: Valuation Allowance	(43,043)	(41,273)
Total deferred tax assets	137,933	151,166
Deferred tax liabilities
Prepaid expense	(8,594)	(9,268)
Property and equipment, net	(3,953)	(903)
Acquired intangibles, net	(145,252)	(160,130)
Total deferred tax liabilities	(157,799)	(170,301)
Net deferred tax liabilities	$ (19,866)	$ (19,135)