Earnings Per Share - Calculation of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 68,145	$ 64,499	$ 215,574	$ 249,340
Weighted-average number of basic shares outstanding during the period	24,866	24,656	24,819	24,588
Dilutive effect of RSUs after application of treasury stock method	482	578	550	641
Weighted-average number of diluted shares outstanding during the period	25,348	25,234	25,369	25,229
Basic earnings per share	$ 2.74	$ 2.62	$ 8.69	$ 10.14
Diluted earnings per share	$ 2.69	$ 2.56	$ 8.50	$ 9.88