Schedule of Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components Of Deferred Tax Assets And Liabilities [Abstract]
Deferred tax assets, Net operating loss carryforwards	$ 841	$ 761
Deferred tax assets, Tax credits	1,839	1,520
Deferred tax assets, Intangible assets	0	10
Deferred tax assets, Deferred revenue adjustment	543	1,214
Deferred tax assets, Accrued Compensation	6,519	2,863
Share-based compensation expense	12,987	11,597
Deferred tax assets, Deferred rent	1,764	0
Deferred tax assets, Other	2,115	2,457
Deferred tax assets before valuation allowance	26,608	20,422
Deferred tax assets, Valuation allowance	(1,507)	(1,015)
Deferred tax assets, net of valuation allowance	25,101	19,407
Deferred tax liabilities, Prepaid expenses and other	1,049	1,301
Deferred tax liabilities, Property and equipment	5,841	6,778
Deferred tax liabilities, Capitalized software development costs	0	695
Method change	932	1,340
Total deferred tax liabilities	7,822	10,114
Total net deferred tax asset	17,279	9,293
Non-current deferred tax assets, net	17,316	9,297
Non-current deferred tax liabilities	$ (37)	$ (4)