EARNINGS PER SHARE - Calculation of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 136,977	$ 120,344	$ 106,478	$ 93,644	$ 93,731	$ 80,577	$ 79,195	$ 67,977	$ 457,443	$ 321,480	$ 265,604
Weighted-average number of basic shares outstanding during the period	23,552	24,935	25,225	25,099	25,089	25,078	25,065	24,894	24,705	25,031	24,833
Dilutive effect of RSUs after application of treasury stock method									287	454	562
Weighted-average number of diluted shares outstanding during the period	23,856	25,166	25,451	25,486	25,496	25,478	25,435	25,532	24,992	25,485	25,395
Basic earnings per share	$ 5.82	$ 4.83	$ 4.22	$ 3.73	$ 3.74	$ 3.21	$ 3.16	$ 2.73	$ 18.52	$ 12.84	$ 10.70
Diluted earnings per share	$ 5.74	$ 4.78	$ 4.18	$ 3.67	$ 3.68	$ 3.16	$ 3.11	$ 2.66	$ 18.30	$ 12.61	$ 10.46