Leases - Schedule of Supplemental Balance Sheet Information Related to Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Operating leases
Right-of-use assets	$ 13,203
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Current lease liabilities	$ 3,809
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherAccruedLiabilitiesCurrent
Non-current lease liabilities	$ 9,407
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Total operating lease liabilities	$ 13,216
Finance leases
Right-of-use assets	$ 106,018
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet
Current lease liabilities	$ 22,695	$ 23,117
Non-current lease liabilities	56,368	$ 61,555
Total finance lease liabilities	$ 79,063
Weighted average lease term
Operating leases	8 years 4 months 9 days
Finance leases	11 years 1 month 24 days
Weighted average discount rate
Operating leases	3.54%
Finance leases	4.98%