Segment Reporting - Revenues and Percentage of Consolidated Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Revenues	$ 1,945,391	$ 1,728,488	$ 1,880,332
Customer Concentration Risk \| Sales Revenue, Net \| Royal Dutch Shell Plc
Revenue, Major Customer [Line Items]
Revenues			$ 259,400
Percentage of consolidated revenues			14.00%
Customer Concentration Risk \| Sales Revenue, Net \| BP plc [Member]
Revenue, Major Customer [Line Items]
Revenues	$ 195,000	$ 195,000	$ 183,000
Percentage of consolidated revenues	11.00%	11.00%	10.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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