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	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation [Abstract]
Number of shares authorized under the plan (in shares)	5,800,000	5,800,000
Number of options granted to date (in shares)	4,774,582	4,159,882
Stock option activity, shares [Roll Forward]
Number of options outstanding at beginning of year (in shares)	1,711,600	1,634,160
Options granted (in shares)	614,700	592,700
Options forfeited (in shares)	(7,000)	(12,500)
Options paid in cash upon vesting (in shares)	(554,200)	(502,760)
Number of options outstanding at period end (in shares)	1,765,100	1,711,600
Stock option related information [Abstract]
Cash paid out on options vested	$ 2,516	$ 1,745
Compensation costs recognized	3,280	2,901
Total liability for the Plan	$ 4,900	$ 4,100
Minimum [Member]
Share-based Compensation [Abstract]
Strike price of phantom stock options as percent of book value	100.00%