Components of Net Periodic Benefit Cost (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2011 acre	Jun. 30, 2012 plan	Jun. 30, 2011	Jun. 30, 2012 plan	Jun. 30, 2011
Components of Net Periodic Benefit Cost
Service cost					$ 18,000
Interest cost		798,000	835,000	1,596,000	1,670,000
Expected return on plan assets		(717,000)	(757,000)	(1,434,000)	(1,513,000)
Amortization of prior service cost			2,000		8,000
Amortization of transition liability			3,000		11,000
Recognized actuarial loss		185,000	202,000	370,000	404,000
Net expense		266,000	285,000	532,000	598,000
Expected minimum required contributions		2,200,000		2,200,000
Contributions funded by employer				1,100,000
Security to support the unfunded liabilities of the Bargaining Plan	5,200,000
Area of property pledged as security (in acres)	1,400
Period for release of property pledged as collateral	5 years
Additional security to support unfunded liabilities		$ 18,700,000		$ 18,700,000
Number of unfunded pension plans		2		2