Revenue Recognition - Summary of Changes to Remaining Performance Obligations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Jan. 01, 2018	Dec. 31, 2017
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations	$ 3,386,673	[1]	$ 3,673,317
Bookings from new contracts	193,170
Additions on existing contracts, net	128,004
Less: Amounts recognized in revenues	$ 607,818
Before ASC 606 Cumulative Effect Adjustment [Member] | ASU 606 [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations				$ 3,901,443
ASC 606 Cumulative Effect Adjustment [Member] | ASU 606 [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations			$ (228,126)

[1] At March 31, 2018, approximately 48% of our RPOs were attributable to Saudi Aramco