Business Operations - Revenues and Percentage of Consolidated Revenue (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Revenue, Major Customer [Line Items] | |||
| Revenue of significant customer | $ 550,543 | $ 534,681 | $ 276,193 |
| Statoil ASA [Member] | Customer Concentration Risk [Member] | |||
| Revenue, Major Customer [Line Items] | |||
| Revenue of significant customer | $ 42,600 | ||