Segment Information - Summary of Revenues on Percentage Basis by Geographic Region (Detail)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	52.00%	67.00%
South America [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	11.00%	10.00%
Japan [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	8.00%	2.00%
Europe [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	19.00%	15.00%
Other [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	10.00%	6.00%