Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Amounts of Non-hedging Derivative Financial Instruments (Detail)

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Summary of Significant Accounting Policies - Schedule of Amounts of Non-hedging Derivative Financial Instruments (Detail) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Forward Purchase Contracts [Member]    
Derivatives, Fair Value [Line Items]    
Asset Derivatives $ 0 $ 3
Liability Derivatives 413 4
Derivatives Not Designated as Hedging Instruments [Member]    
Derivatives, Fair Value [Line Items]    
Asset Derivatives   3
Liability Derivatives 413 4
Derivatives Not Designated as Hedging Instruments [Member] | Forward Purchase Contracts [Member] | Prepaid Expenses and Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Asset Derivatives   3
Derivatives Not Designated as Hedging Instruments [Member] | Forward Purchase Contracts [Member] | Accrued Liabilities Current [Member]    
Derivatives, Fair Value [Line Items]    
Liability Derivatives $ 413 $ 4