Employee Benefit Plan Obligations (Details 7)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Weighted Average Assumptions Used to Determine Benefit Obligations at Measurement Date
Discount rate	4.30%	5.20%	5.70%
Rate of compensation increases		3.50%	3.50%
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost for Years ended December 31
Discount rate	5.20%	5.70%	6.10%
Expected long-term return on plan assets	7.75%	8.00%	8.25%
Rate of compensation increases	3.50%	3.50%	4.50%
Postretirement Benefits [Member]
Weighted Average Assumptions Used to Determine Benefit Obligations at Measurement Date
Discount rate	4.30%	5.30%	5.80%
Rate of compensation increases
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost for Years ended December 31
Discount rate	5.30%	5.80%	6.10%