Employee Benefit Plans - Additional Information (Detail) NOK in Millions	3 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 NOK	Jun. 30, 2016 USD ($)	Jun. 30, 2016 NOK
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions	$ 0		$ 0
Expected contribution to the plan during the remaining quarters of fiscal 2018	0
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions	0		100,000
Expected contribution to the plan during the remaining quarters of fiscal 2018	100,000
Norway’s Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions	400,000	NOK 3.0	$ 500,000	NOK 3.4
Expected contribution to the plan during the remaining quarters of fiscal 2018	$ 0