Stock-Based Compensation, Phantom Stock Option Plan and Long-term Incentive Plan (Details) - 2011 Phantom Stock Option and Long-term Incentive Plan [Member] - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Stock option activity, shares [Roll Forward]
Number of options outstanding at beginning of year (in shares)	1,765,100	1,711,600
Options granted (in shares)	523,700	614,700
Options forfeited (in shares)	0	(7,000)
Number of options outstanding at period end (in shares)	2,288,800	2,319,300
Stock option related information [Abstract]
Compensation expense recognized	$ 635	$ 645
Total liability for the Plan	$ 5,500		$ 4,900