Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Operating lease, liability	$ 19,647
Operating lease right-of-use assets	20,663
Retained earnings	$ (272,602)		$ (201,025)
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, liability		$ 20,600
Operating lease right-of-use assets		22,300
ASU 2016-02 [Member] | Restatement Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Retained earnings		$ 300