LEASES: Lease Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Mar. 31, 2020
Leases [Abstract]
Right-of-use asset (see Note 4)	$ 12,536	$ 17,830
Operating lease, right-of-use asset, statement of financial position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Short-term lease liabilities (see Note 4)	$ 9,590	$ 9,641
Operating lease, liability, current, statement of financial position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Long-term lease liabilities	$ 5,309	$ 11,449
Operating lease, liability, noncurrent, statement of financial position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent