Industry and Geographic Information - Sales to Individual Customers in Excess of 10% of Total Revenue (Detail) - Sales [Member] - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Sales percentage	68.00%	51.00%	49.00%
A
Revenue, Major Customer [Line Items]
Sales percentage	29.00%	13.00%	12.00%
B
Revenue, Major Customer [Line Items]
Sales percentage	16.00%	18.00%	19.00%
C
Revenue, Major Customer [Line Items]
Sales percentage	13.00%	5.00%	5.00%
D
Revenue, Major Customer [Line Items]
Sales percentage	10.00%	15.00%	13.00%