Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Pension Plans [Member]
Components of Net Periodic Benefit Costs [Abstract]
Service cost	$ 3,251	$ 3,137
Interest cost	1,470	1,225
Expected return on plan assets	(2,616)	(2,298)
Prior service cost (credit) amortization	72	48
Actuarial loss (gain) amortization	513	897
Net periodic benefit costs (credit)	2,690	3,009
Postretirement Benefit Plans [Member]
Components of Net Periodic Benefit Costs [Abstract]
Service cost	19	23
Interest cost	82	80
Prior service cost (credit) amortization	(85)	(98)
Actuarial loss (gain) amortization	(81)	(78)
Net periodic benefit costs (credit)	$ (65)	$ (73)