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Employee Benefit Plans - Additional Information (Detail) kr in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
May 31, 2018 USD ($) | Jun. 30, 2018 USD ($) | Jun. 30, 2018 NOK (kr) | Jun. 30, 2017 USD ($) | Jun. 30, 2017 NOK (kr) | Jun. 30, 2018 USD ($) | Jun. 30, 2018 NOK (kr) | Jun. 30, 2017 USD ($) | Jun. 30, 2017 NOK (kr)
President, and Chief Executive Officer [Member] | Supplemental Executive Retirement Plan |  |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |  |
Settlement of distribution | $ 8,900,000 |  |  |  |  |  |  |  |
Settlement loss |  | $ 300,000 |  |  |  |  |  |  |
Pension Plans, Defined Benefit |  |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |  |
Defined benefit plan, employer contributions |  | 0 |  | $ 0 |  | $ 0 |  | $ 0 |
Supplemental Executive Retirement Plan |  |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |  |
Defined benefit plan, employer contributions |  | 40,000 |  | 0 |  | 300,000 |  | 0 |
Expected contribution to the plan during the remaining quarters of fiscal 2018 |  | 700,000 |  |  |  | 700,000 |  |  |
Norway’s Defined Benefit Pension Plan |  |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |  |
Defined benefit plan, employer contributions |  | 200,000 | kr 1.9 | $ 400,000 | kr 3.0 | 200,000 | kr 1.9 | $ 400,000 | kr 3.0
Expected contribution to the plan during the remaining quarters of fiscal 2018 |  | $ 0 |  |  |  | $ 0 |  |  |

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