SEGMENT INFORMATION, REVENUES BY GEOGRAPHY AND SIGNIFICANT CUSTOMERS - Revenues by product (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2017
Segment Reporting Information [Line Items]                      
Total revenues $ 286,641 $ 284,911 $ 307,276 $ 282,905 $ 269,778 $ 250,404 $ 250,811 $ 245,868 $ 1,161,733 $ 1,016,861 $ 865,268
Percentage of revenues                 100.00% 100.00% 100.00%
Revenue                      
Segment Reporting Information [Line Items]                      
Percentage of revenues                 100.00% 100.00% 100.00%
Service Provider Technology                      
Segment Reporting Information [Line Items]                      
Total revenues                 $ 428,490 $ 446,600 $ 455,598
Service Provider Technology | Revenue                      
Segment Reporting Information [Line Items]                      
Percentage of revenues                 37.00% 44.00% 53.00%
Enterprise Technology                      
Segment Reporting Information [Line Items]                      
Total revenues                 $ 733,243 $ 570,261 $ 409,670
Enterprise Technology | Revenue                      
Segment Reporting Information [Line Items]                      
Percentage of revenues                 63.00% 56.00% 47.00%