Employee Benefit Plans (Details 8)	12 Months Ended
	Dec. 31, 2012 Equity Securities	Dec. 31, 2012 Debt Securities	Dec. 31, 2012 Cash	Dec. 31, 2012 Commodities	Dec. 31, 2012 Pension Benefit Plan	Dec. 31, 2011 Pension Benefit Plan	Dec. 31, 2012 Pension Benefit Plan Equity Securities	Dec. 31, 2011 Pension Benefit Plan Equity Securities	Dec. 31, 2012 Pension Benefit Plan Debt Securities	Dec. 31, 2011 Pension Benefit Plan Debt Securities	Dec. 31, 2012 Pension Benefit Plan Cash	Dec. 31, 2011 Pension Benefit Plan Cash	Dec. 31, 2012 Pension Benefit Plan Commodities	Dec. 31, 2011 Pension Benefit Plan Commodities	Dec. 31, 2012 Other Benefits Plan	Dec. 31, 2011 Other Benefits Plan	Dec. 31, 2012 Other Benefits Plan Equity Securities	Dec. 31, 2011 Other Benefits Plan Equity Securities	Dec. 31, 2012 Other Benefits Plan Debt Securities	Dec. 31, 2011 Other Benefits Plan Debt Securities	Dec. 31, 2012 Other Benefits Plan Cash	Dec. 31, 2011 Other Benefits Plan Cash	Dec. 31, 2012 Other Benefits Plan Commodities	Dec. 31, 2011 Other Benefits Plan Commodities
Allocation of plan assets					100.00%	100.00%	60.90%	61.60%	32.90%	31.30%	6.00%	6.90%	0.20%	0.20%	100.00%	100.00%	40.30%	37.00%	53.00%	57.80%	5.90%	4.60%	0.80%	0.60%
Target plan allocations	60.00%	38.00%	2.00%	0.00%
Target plan allocations, minimum	30.00%	25.00%	0.00%	0.00%
Target plan allocations, maximum	65.00%	70.00%	10.00%	0.00%