Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Summary of Fair Value Measurements (Detail)

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Summary of Significant Accounting Policies - Summary of Fair Value Measurements (Detail) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Asset at Fair Value:    
Total Assets at Fair Value   $ 3
Liabilities at Fair Value    
Total Liabilities at Fair Value $ 413 4
Forward Purchase Contracts [Member]    
Asset at Fair Value:    
Forward purchase contracts 0 3
Liabilities at Fair Value    
Forward purchase contracts 413 4
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]    
Asset at Fair Value:    
Total Assets at Fair Value   3
Liabilities at Fair Value    
Total Liabilities at Fair Value 413 4
Fair Value, Measurements, Recurring [Member] | Forward Purchase Contracts [Member] | Level 2 [Member]    
Asset at Fair Value:    
Forward purchase contracts   3
Liabilities at Fair Value    
Forward purchase contracts $ 413 $ 4