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				9 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014		Mar. 31, 2013
Pension Plan
Components of net periodic benefit cost
Service cost	$ 100		$ 119		$ 300		$ 357
Interest cost	1,452		1,449		4,356		4,347
Expected return on plan assets	(1,705)		(1,660)		(5,115)		(4,980)
Amortization of net (gain) loss	336	[1]	387	[1]	1,008	[1]	1,161	[1]
Amortization of prior service cost (credit)	0		5		0		15
Net periodic benefit (credit) cost	183		300		549		900
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	234		493		702		986
Interest cost	202		242		607		484
Expected return on plan assets	0		0		0		0
Amortization of net (gain) loss	(220)		4		(661)		8
Amortization of unrecognized transition (asset) obligation	0		0		0		0
Amortization of prior service cost (credit)	(440)		(439)		(1,319)		(878)
Net periodic benefit (credit) cost	$ (224)		$ 300		$ (671)		$ 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 loss and net prior service cost remaining in AOCI that is expected to be recognized as a component of net periodic benefit cost over the current fiscal year.