Employee Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure
Interest cost		$ 3,437	$ 4,236
Amortization of net gain		2,010	1,479
Net periodic benefit cost		1,296	1,309
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure
Service cost	$ 530	19	446
Interest cost	887	293	725
Amortization of net gain	(834)	(5,296)	(3,067)
Curtailment credit - Retiree Medical	0	0	5,750
Amortization of prior service credit	(1,757)	(8,961)	(5,666)
Settlement credit - Retiree Medical	0	(6,669)	0
Net periodic benefit cost	$ (1,174)	$ (20,614)	$ (13,312)