Summary of Significant Accounting Policies - Schedule of Customers Representing Greater than 10% of Accounts Receivable and Revenue (Detail) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue | Customer D
Concentration Risk [Line Items]
Percentage of concentration risk			23.00%
Revenue | Customer F
Concentration Risk [Line Items]
Percentage of concentration risk		16.00%
Revenue | Customer G
Concentration Risk [Line Items]
Percentage of concentration risk			25.00%
Revenue | Customer H
Concentration Risk [Line Items]
Percentage of concentration risk		17.00%
Revenue | Customer I
Concentration Risk [Line Items]
Percentage of concentration risk		17.00%
Revenue | Customer J
Concentration Risk [Line Items]
Percentage of concentration risk		16.00%
Revenue | Customer K
Concentration Risk [Line Items]
Percentage of concentration risk		14.00%
Revenue | Customer L
Concentration Risk [Line Items]
Percentage of concentration risk		10.00%
Revenue | Customer N
Concentration Risk [Line Items]
Percentage of concentration risk			47.00%
Accounts Receivable | Customer A
Concentration Risk [Line Items]
Percentage of concentration risk	23.00%
Accounts Receivable | Customer B
Concentration Risk [Line Items]
Percentage of concentration risk	22.00%
Accounts Receivable | Customer C
Concentration Risk [Line Items]
Percentage of concentration risk	19.00%
Accounts Receivable | Customer D
Concentration Risk [Line Items]
Percentage of concentration risk	16.00%
Accounts Receivable | Customer E
Concentration Risk [Line Items]
Percentage of concentration risk	15.00%
Accounts Receivable | Customer F
Concentration Risk [Line Items]
Percentage of concentration risk		24.00%
Accounts Receivable | Customer K
Concentration Risk [Line Items]
Percentage of concentration risk		16.00%
Accounts Receivable | Customer M
Concentration Risk [Line Items]
Percentage of concentration risk		36.00%