GOODWILL AND INTANGIBLE ASSETS: - Amounts allocated to intangible assets from acquisitions (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Developed technology, gross (Software)	$ 115,300	$ 113,600
Accumulated amortization	(88,131)	(85,008)
Total finite-lived intangible assets, net	27,169	28,592
Developed technology, gross (Software)
Finite-Lived Intangible Assets [Line Items]
Developed technology, gross (Software)	55,500	54,000
Accumulated amortization	(50,385)	(49,625)
Total finite-lived intangible assets, net	5,115	4,375
Trade name
Finite-Lived Intangible Assets [Line Items]
Developed technology, gross (Software)	36,000	35,800
Accumulated amortization	(27,499)	(26,128)
Total finite-lived intangible assets, net	8,501	9,672
Publisher Relationship
Finite-Lived Intangible Assets [Line Items]
Developed technology, gross (Software)	23,800	23,800
Accumulated amortization	(10,247)	(9,255)
Total finite-lived intangible assets, net	$ 13,553	$ 14,545
Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period	2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period	6 years