Pension Plan and Postretirement Benefits Other Than Pension (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits
Pension Plan and Postretirement Benefits Other than Pension
Aggregate liability to participants	$ 45,000,000	$ 12,300,000
Other Postretirement Benefits
Pension Plan and Postretirement Benefits Other than Pension
Initial health care cost trend rate (as a percent)	9.51%	10.00%	9.00%
Number of years at which the rate reaches the ultimate trend rate (in years)	16
Rate to which the cost trend rate is assumed to decline (as a percent)	4.50%
Effect of 1% annual increase in assumed health care cost trend rates on the accumulated postretirement benefit obligation	1,000,000
Effect of 1% annual increase in assumed health care cost trend rates on the service and interest cost components	137,000
Effect of 1% annual decrease in assumed health care cost trend rates on the accumulated postretirement benefit obligation	866,000
Effect of 1% annual decrease in assumed health care cost trend rates on the service and interest cost components	115,000
Aggregate liability to participants	7,800,000	6,500,000
Current portion of postretirement liability	289,000	303,000	250,000
SERP
Pension Plan and Postretirement Benefits Other than Pension
Percentage of executive's base salary that is used to credit participants SERP accounts	4.00%
Aggregate liability to participants	$ 3,700,000	$ 3,700,000