Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 4,500,000		$ 4,500,000
Topic 606
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings		$ 0
ASU 2016-18
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 4,500,000			$ 5,100,000