ACCUMULATED OTHER COMPREHENSIVE LOSS (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2016
Cost of revenues	$ 159,097	$ 618,001	$ 392,279	$ 337,887
Research and development	20,279	82,245	54,966	33,231
Sales and marketing	20,444	68,307	50,032	34,833
General and administrative	6,790	29,264	18,682	12,133
Financial income (expenses), net	(2,789)	(2,297)	9,158	471
Total, before income taxes	30,598	137,123	100,244	72,230
Income tax expense	5,217	9,077	16,072	(4,379)
Total, net of income taxes	25,381	128,833	84,172	76,609
Total, net of income taxes	(317)	106	(994)	(168)
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Cost of revenues	47	3	166	30
Research and development	227	19	570	115
Sales and marketing	58	5	151	33
General and administrative	46	4	153	24
Total, before income taxes	378	31	1,040	202
Income tax expense	61		46	33
Total, net of income taxes	317	31	994	169
Available-for-sale Securities [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Financial income (expenses), net		(137)		(1)
Income tax expense
Total, net of income taxes		(137)		(1)
Total, net of income taxes	$ 317	$ (106)	$ 994	$ 168