Summary of Significant Accounting Policies - Summary of Sales to Largest Customers (Parenthetical) (Detail) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member] - Customer Three [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage		26.00%	21.00%	32.00%
Maximum [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	10.00%