Employee Benefit Plans Weighted Average Discount Rate Used to Determine the Net Periodic Postretirement Benefit Costs (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Net periodic postretirement benefit costs	4.25%	5.25%	5.75%
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net periodic postretirement benefit costs	3.75%	5.25%	5.75%
Accumulated postretirement benefit obligations	3.50%	3.75%	5.25%