Summary of Significant Accounting Policies and New Accounting Standards (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Net income	$ 13,417	$ 30,178	$ 25,594	$ 48,931
Weighted average number of shares - basic (in shares)	39,411	39,163	39,409	39,128
Dilutive effect of stock options	591	815	545	867
Weighted average number of shares - diluted (in shares)	40,002	39,978	39,954	39,995
Net income per share
basic (in dollars per share)	$ 0.34	$ 0.77	$ 0.65	$ 1.25
diluted (in dollars per share)	$ 0.34	$ 0.75	$ 0.64	$ 1.22