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, 2018	Mar. 31, 2018	Dec. 31, 2017	[1]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 51,831	$ 64,499	$ 142,795		$ 42,046	$ 44,231	$ 40,357	$ 42,420	$ 36,663	$ 301,171	$ 163,671	$ 142,799
Weighted-average number of basic shares outstanding during the period	24,700	24,656	24,622		24,487	24,459	24,419	24,387	24,340	24,616	24,401	24,262
Dilutive effect of SSARs/stock options and RSUs/restricted shares after application of treasury stock method										639	668	540
Weighted-average number of diluted shares outstanding during the period	25,331	25,234	25,211		25,243	25,172	25,106	25,069	24,928	25,255	25,069	24,802
Basic earnings per share	$ 2.10	$ 2.62	$ 5.80		$ 1.72	$ 1.81	$ 1.65	$ 1.74	$ 1.51	$ 12.23	$ 6.71	$ 5.89
Diluted earnings per share	$ 2.05	$ 2.56	$ 5.66		$ 1.67	$ 1.76	$ 1.61	$ 1.69	$ 1.47	$ 11.93	$ 6.53	$ 5.76

[1] Net income for the second quarter of FY2018 includes a net benefit related to the TCJA. See Note 19.