Summary of Significant Accounting Policies and New Accounting Standards (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Net income	$ 64,883	$ 64,615	$ 82,728
Weighted average number of shares - basic	40,181	39,524	39,254
Dilutive effect of stock options and restricted stock units	204	518	708
Weighted average number of shares - diluted	40,385	40,042	39,962
Net income per share
basic (in dollars per share)	$ 1.61	$ 1.63	$ 2.11
diluted (in dollars per share)	$ 1.61	$ 1.61	$ 2.07