Employee Benefit Plans - Components of Net Periodic Benefit Costs (Details) - Other Postretirement Benefits Plan - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure
Service cost	$ 760	$ 1,388	$ 1,195
Interest cost	829	1,194	943
Amortization of net gain	(630)	(196)	(500)
Amortization of prior service credit	(1,757)	(1,757)	(1,757)
Net periodic benefit cost	$ (798)	$ 629	$ (119)