Recent Accounting Pronoucements - Schedule of Adjustments in Balance Sheet due to Adoption of ASC 842 (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Jan. 01, 2019		Dec. 31, 2018
Adjustments For Change In Accounting Principle [Line Items]
Operating lease and right-of-use assets		$ 11,448	$ 11,711	[1]
Deferred rent					$ 390
Deferred rent non-current					3,922
Operating lease liabilities		15,832	1,175	[2]
Non-current operating lease liabilities		$ 14,457	14,848	[2]
Previously Reported [Member]
Adjustments For Change In Accounting Principle [Line Items]
Deferred rent	[3]				390
Deferred rent non-current	[3]				$ 3,922
Restatement Adjustment [Member]
Adjustments For Change In Accounting Principle [Line Items]
Operating lease and right-of-use assets	[1]		11,711
Deferred rent	[3]		(390)
Deferred rent non-current	[3]		(3,922)
Operating lease liabilities	[2]		1,175
Non-current operating lease liabilities	[2]		$ 14,848

[1] Represents capitalization of operating lease right-of-use assets, offset by reclassification of deferred rent and tenant incentives to operating lease right-of-use assets

[2] Represents recognition of operating lease liabilities.

[3] Represents reclassification of deferred rent and tenant incentives to operating lease right-of-use assets.