Employee Benefit Plans - Net periodic pension expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Service cost - benefits earned during the period	$ 735	$ 739	$ 2,204	$ 2,217
Interest cost on benefit obligation	723	654	2,170	1,963
Expected return on plan assets	(794)	(707)	(2,382)	(2,121)
Amortization of net actuarial (gain) loss and prior service costs	446	351	1,338	1,053
Net periodic pension expense	$ 1,110	$ 1,037	$ 3,330	$ 3,112