SEGMENT INFORMATION, REVENUES BY GEOGRAPHY AND SIGNIFICANT CUSTOMERS - Revenues by product (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2018
Segment Reporting Information [Line Items]                      
Total revenues $ 315,522 $ 337,417 $ 308,284 $ 323,277 $ 286,641 $ 284,911 $ 307,276 $ 282,905 $ 1,284,500 $ 1,161,733 $ 1,016,861
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                 $ 442,023 $ 428,490 $ 446,600
Service Provider Technology | Revenue                      
Segment Reporting Information [Line Items]                      
Percentage of revenues                 34.00% 37.00% 44.00%
Enterprise Technology                      
Segment Reporting Information [Line Items]                      
Total revenues                 $ 842,477 $ 733,243 $ 570,261
Enterprise Technology | Revenue                      
Segment Reporting Information [Line Items]                      
Percentage of revenues                 66.00% 63.00% 56.00%