Benefits 9 Parentheticals (Details)	Dec. 31, 2011	Dec. 31, 2010
Pension member
Benefits [Line Items]
Large-cap U.S. equities	36.00%	38.00%
Small-cap U.S. equities	6.00%	8.00%
International equities	20.00%	20.00%
Fixed income securities	30.00%	29.00%
Other investments	8.00%	5.00%
OPEB member
Benefits [Line Items]
Large-cap U.S. equities	19.00%	17.00%
Small-cap U.S. equities	2.00%	4.00%
International equities	10.00%	10.00%
Fixed income securities	55.00%	57.00%
Other investments	6.00%	2.00%
Cash fund investments	8.00%	10.00%