Employee Benefit Plans - Amortization Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Retiree Medical Plan
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit) [Roll Forward]
Net Prior Service Cost (Credit), beginning of period	$ (15,720)
Annual Amortization	1,757
Net Prior Service Cost (Credit), end of period	(13,963)	$ (15,720)
Amortization of Net (Gain) Loss Calculation
Net (gain) loss	(3,655)	(8,006)
Net (gain) loss subject to amortization	(3,655)	(8,006)
Corridor (10% of greater of APBO or assets)	1,723	1,262
Net (gain)/loss in excess of corridor	$ (1,932)	$ (6,744)
Amortization years	09 years 09 months 18 days	10 years 08 months 12 days
Other Postretirement Benefit Plans, Defined Benefit Plan Established January 1, 2008 [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit) [Roll Forward]
Net Prior Service Cost (Credit), beginning of period	$ (1,193)
Annual Amortization	$ 230
Years Remaining	5 years 2 months 12 days
Curtailment	$ 0
Net Prior Service Cost (Credit), end of period	(963)	$ (1,193)
Other Postretirement Benefit Plans, Defined Benefit Plan Established July 1, 2012 [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit) [Roll Forward]
Net Prior Service Cost (Credit), beginning of period	(14,527)
Annual Amortization	$ 1,527
Years Remaining	9 years 6 months
Curtailment	$ 0
Net Prior Service Cost (Credit), end of period	(13,000)	(14,527)
Death Benefit Plan
Amortization of Net (Gain) Loss Calculation
Net (gain) loss	690	1,791
Net (gain) loss subject to amortization	690	1,791
Corridor (10% of greater of APBO or assets)	(729)	(826)
Net (gain)/loss in excess of corridor	$ (39)	$ 965
Amortization years	07 years 08 months 12 days	7 years 04 months 24 days