STOCK BASED COMPENSATION - Summary of RSU activity (Details) - Restricted stock units - $ / shares
12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2018
Number of Shares      
Non-vested RSUs, beginning balance (in shares) 112,786 144,100 180,373
RSUs granted (in shares) 20,333 49,965 69,188
RSUs vested (in shares) (42,801) (53,443) (78,358)
RSUs forfeited (in shares) (7,747) (27,836) (27,103)
Non-vested RSUs, ending balance (in shares) 82,571 112,786 144,100
Weighted Average Grant Date Fair Value      
Non-vested RSUs, weighted average grant date fair value, beginning balance (in dollars per share) $ 73.24 $ 53.24 $ 40.51
RSUs granted, weighted average grant date fair value (in dollars per share) 157.68 92.77 64.66
RSUs vested, weighted average grant date fair value (in dollars per share) 61.28 43.67 38.09
RSUs forfeited, weighted average grant date fair value (in dollars per share) 80.30 61.55 41.45
Non-vested RSUs, weighted average grant date fair value, ending balance (in dollars per share) $ 99.57 $ 73.24 $ 53.24