Segment Information - Summary of Revenues on Percentage Basis by Geographic Region (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	100.00%	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	63.00%	78.00%	62.00%
South America [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	10.00%	7.00%	11.00%
Japan [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	5.00%	2.00%	2.00%
Europe [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	15.00%	9.00%	18.00%
Other [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	7.00%	4.00%	7.00%