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				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2013		Mar. 31, 2012		Jun. 30, 2012
Defined Benefit Pension Plans
Components of net periodic benefit cost
Service cost	$ 119		$ 124		$ 357		$ 371
Interest cost	1,449		1,525		4,347		4,575
Expected return on plan assets	(1,660)		(1,703)		(4,980)		(5,108)
Amortization of net loss (gain)	387	[1]	342	[1]	1,161	[1]	1,027	[1]
Amortization of net prior service cost (credit)	5	[1]	5	[1]	15	[1]	14	[1]
Net periodic postretirement benefit cost	300		293		900		879
Weighted average assumptions used to determine benefit obligations
Discount rate					4.55%				5.60%
Expected long-term rate of return					8.00%				8.25%
Rate of compensation increase					0.00%	[2]			3.00%	[2]
Other Postretirement Benefits
Components of net periodic benefit cost
Service cost	634		409		1,903		1,227
Interest cost	178		330		534		990
Amortization of net loss (gain)	(218)		(199)		(653)		(597)
Amortization of net prior service cost (credit)	(240)		(58)		(720)		(174)
Net periodic postretirement benefit cost	$ 354		$ 482		$ 1,064		$ 1,446
Weighted average assumptions used to determine benefit obligations
Discount rate					4.40%				5.46%

[1] These amounts represent the estimated portion of the net loss and net prior service cost remaining in accumulated other comprehensive income that is expected to be recognized as a component of net periodic benefit cost over the current fiscal year.

[2] For Hourly Employees' Plan only.