OTHER ACCRUED EXPENSES: (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Mar. 31, 2020
Business Acquisition [Line Items]
Liabilities of non-qualified retirement plan	$ 16,425	$ 11,623
Accrued Data Marketplace expenses	18,955	12,023
Short-term lease liabilities (see Note 4)	9,590	9,641
Other miscellaneous accrued expenses	9,781	13,201
Other accrued expenses	72,480	68,991
Pacific Data Partners LLC
Business Acquisition [Line Items]
Business combination, contingent consideration, liability	12,239	16,318
Other accrued expenses	12,200
Data Plus Math Corporation
Business Acquisition [Line Items]
Business combination, contingent consideration, liability	4,061	6,185
Acuity Data
Business Acquisition [Line Items]
Business combination, contingent consideration, liability	$ 1,429	$ 0