ACQUISITIONS: - Purchase price allocation related to assets acquired and liabilities assumed (Details) - USD ($) $ in Thousands			12 Months Ended
	Feb. 14, 2018	Nov. 29, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Dec. 01, 2015	Nov. 29, 2015
Business Acquisition [Line Items]
Goodwill			$ 595,995	$ 592,731	$ 492,745
Net cash paid			$ 4,478	$ 137,383	$ 5,386
Allant Television Division
Business Acquisition [Line Items]
Trade accounts receivable						$ 499
Goodwill						1,377
Total assets acquired						5,976
Net assets acquired						5,386
Accounts payable						(590)
Arbor and Circulate
Business Acquisition [Line Items]
Cash		$ 9,495
Trade accounts receivable		3,352
Other current and noncurrent assets		278
Goodwill		105,670
Intangible assets (Other assets)		40,800					$ 40,800
Total assets acquired		159,595
Deferred income taxes		8,093
Accounts payable and accrued expenses		(4,623)
Net assets acquired		146,879
Net cash paid		$ 137,384
Pacific Data Partners LLC
Business Acquisition [Line Items]
Cash	$ 228
Trade accounts receivable	224
Goodwill	3,260
Total assets acquired	5,912
Accounts payable and accrued expenses	(706)
Net assets acquired	5,206
Funds held in escrow	(500)
Net cash paid	4,478
Developed technology (Software, net) | Allant Television Division
Business Acquisition [Line Items]
Finite-lived intangibles						2,700
Developed technology (Software, net) | Pacific Data Partners LLC
Business Acquisition [Line Items]
Finite-lived intangibles	2,000
Intangible assets (Other assets) | Allant Television Division
Business Acquisition [Line Items]
Finite-lived intangibles						$ 1,400
Intangible assets (Other assets) | Pacific Data Partners LLC
Business Acquisition [Line Items]
Intangible assets (Other assets)	$ 200