Employee Benefit Plans (Target and Actual Asset Allocations) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Actual asset allocation	100.00%	100.00%
Target allocation	100.00%
Veba I [Member]
Actual asset allocation	100.00%	100.00%
Target allocation	100.00%
Veba II [Member]
Actual asset allocation		100.00%
U S Equity Securities [Member]
Actual asset allocation	28.00%	30.00%
Target allocation, equity securities	28.00%
U S Equity Securities [Member] | Veba I [Member]
Actual asset allocation	20.00%	22.00%
Target allocation, equity securities	30.00%
U S Equity Securities [Member] | Veba II [Member]
Actual asset allocation		1.00%
Non U S Equity Securities [Member]
Actual asset allocation	15.00%	19.00%
Target allocation, equity securities	15.00%
Global Equity Securities [Member]
Actual asset allocation	9.00%	10.00%
Target allocation, equity securities	10.00%
Cash And Cash Equivalents [Member] | Veba I [Member]
Actual asset allocation	49.00%	44.00%
Target allocation	25.00%
Cash And Cash Equivalents [Member] | Veba II [Member]
Actual asset allocation		30.00%
Debt Securities [Member]
Actual asset allocation	32.00%	27.00%
Target allocation, debt securities	32.00%
Debt Securities [Member] | Veba I [Member]
Actual asset allocation	31.00%	34.00%
Target allocation, debt securities	45.00%
Debt Securities [Member] | Veba II [Member]
Actual asset allocation		69.00%
Global Private Equity Securities [Member]
Actual asset allocation	1.00%
Target allocation, equity securities	3.00%
Hedge Funds [Member]
Actual asset allocation	3.00%	3.00%
Target allocation	4.00%
Real Estate And Cash [Member]
Actual asset allocation	9.00%	7.00%
Target allocation	4.00%
Other Global Securities [Member]
Actual asset allocation	3.00%	4.00%
Target allocation	4.00%