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				12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Jun. 30, 2012
Defined Benefit Pension Plans
Components of net periodic benefit cost
Service cost	$ 119		$ 124		$ 238		$ 248
Interest cost	1,449		1,525		2,898		3,050
Expected return on plan assets	(1,660)		(1,703)		(3,320)		(3,406)
Amortization of net loss (gain)	387	[1]	342	[1]	774	[1]	685	[1]
Amortization of net prior service cost (credit)	5	[1]	5	[1]	10	[1]	10	[1]
Net periodic postretirement benefit cost	300		293		600		587
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	860		409		1,269		818
Interest cost	26		330		356		660
Expected return on plan assets	0		0		0		0
Amortization of net loss (gain)	(236)		(199)		(435)		(398)
Amortization of unrecognized transition (asset) obligation	0		0		0		0
Amortization of net prior service cost (credit)	(422)		(58)		(480)		(116)
Net periodic postretirement benefit cost	$ 228		$ 482		$ 710		$ 964
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.