Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Accruals and reserves, net	$ 26,126	$ 22,305
Allowance for doubtful accounts	7,741	12,386
Stock-based compensation, net	12,654	15,939
Deferred revenue	12,466	15,092
Net operating loss carryforwards	67,677	91,859
Research and development tax credit	38,310	32,952
AMT credits	7,901	7,085
State tax credits	3,795	2,911
Other	11,106	15,065
Less: Valuation Allowance	(79,732)	(23,761)
Total deferred tax assets	150,746	191,833
Capital loss carryforwards	42,702	0
Deferred tax liabilities
Prepaid expense	(6,407)	(9,532)
Property and equipment, net	(13,201)	(15,879)
Acquired intangibles, net	(219,559)	(305,361)
Other	(648)	(22)
Total deferred tax liabilities	(239,815)	(330,794)
Net deferred tax liabilities	$ (89,069)	$ (138,961)