Business Segment and Significant Customer Information - Summary of Revenue by Country (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Entity Wide Revenue Major Customer [Line Items]
Revenues		$ 57,663	$ 42,049
Congo
Entity Wide Revenue Major Customer [Line Items]
Revenues		35,853	26,875
Malaysia
Entity Wide Revenue Major Customer [Line Items]
Revenues			7,923
India
Entity Wide Revenue Major Customer [Line Items]
Revenues		6,530
Qatar
Entity Wide Revenue Major Customer [Line Items]
Revenues			5,784
Other countries
Entity Wide Revenue Major Customer [Line Items]
Revenues	[1]	$ 15,280	$ 1,467

[1] Other countries represent countries in which we operate that individually had operating revenues representing less than 10% of total revenues earned.