Segment Information - Summary of Revenues on Percentage Basis by Geographic Region (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	100.00%	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	66.00%	72.00%	67.00%	66.00%
South America [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	12.00%	10.00%	11.00%	10.00%
Japan [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	3.00%	2.00%	3.00%	2.00%
Europe [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	12.00%	11.00%	14.00%	16.00%
Other [Member]
Segment Reporting Information [Line Items]
Revenues on a percentage basis by geographic region, based on the country	7.00%	5.00%	5.00%	6.00%