Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 1,713	$ 11,366	$ 11,530	$ 11,715	$ 19,982	$ 14,322	$ 24,608	$ 46,019
Denominator:
Weighted-average shares, basic (in shares)	25,346,000			25,704,000			25,386,000	25,647,000
Dilutive effect of share-based payments (in shares)	17,000			58,000			58,000	108,000
Weighted-average shares, diluted (in shares)	25,363,000			25,762,000			25,444,000	25,755,000
Net income per common share, basic (in dollars per share)	$ 0.07			$ 0.46			$ 0.97	$ 1.79
Net income per common share, diluted (in dollars per share)	$ 0.07			$ 0.45			$ 0.97	$ 1.79
Weighted average shares excluded from the computation of diluted earnings per share (in shares)	1,036,740			592,411			980,803	459,189