Employee Benefit Plans - Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2013		Dec. 31, 2012
Pension Plan
Components of net periodic benefit cost
Service cost	$ 100		$ 119		$ 200		$ 238
Interest cost	1,452		1,449		2,904		2,898
Expected return on plan assets	(1,705)		(1,660)		(3,410)		(3,320)
Amortization of net (gain) loss	336	[1]	387	[1]	672	[1]	774	[1]
Amortization of prior service cost (credit)	0		5		0		10
Net periodic benefit cost	183		300		366		600
Weighted average assumptions used to determine benefit obligations
Discount rate					4.50%		4.55%
Expected long-term return on plan assets					8.00%		8.00%
Postretirement Benefits Other Than Pension
Components of net periodic benefit cost
Service cost	(25)		493		468		986
Interest cost	163		242		405		484
Expected return on plan assets	0		0		0		0
Amortization of net (gain) loss	(445)		4		(441)		8
Amortization of unrecognized transition (asset) obligation	0		0		0		0
Amortization of prior service cost (credit)	(440)		(439)		(879)		(878)
Net periodic benefit cost	$ (747)		$ 300		$ (447)		$ 600
Retiree Medical Plan
Weighted average assumptions used to determine benefit obligations
Discount rate					4.80%		4.20%
Death Benefit Plan
Weighted average assumptions used to determine benefit obligations
Discount rate					4.53%		4.39%

[1] These amounts represent the estimated portion of the net (gain) loss and net prior service cost (credit) remaining in AOCI that is expected to be recognized as a component of net periodic benefit cost over the current fiscal year.