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Commitments and Contingencies - Concentrations of Credit Risk (Detail) - Customer Concentration Risk - Customer | 9 Months Ended |
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Concentration Risk [Line Items] |  |  |
Number of customers representing ten percent or more of net receivable position | 0 |  | 0
Number of customers representing ten percent or more of revenue | 0 |  |
Oil and Gas Infrastructure Services Segment |  |  |
Concentration Risk [Line Items] |  |  |
Number of customers representing ten percent or more of revenue |  | 1 |
Consolidated Revenues | Oil and Gas Infrastructure Services Segment |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk percentage |  | 10.00% |

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