Employee Benefit Plans (Fair Value Measurements of Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Total Assets	$ 4,842	$ 4,901
Net receivables and payables	27	23
Pending investment sales, net	3	(139)
Partnership Interest [Member]
Total Assets	127	108
Level 1 [Member]
Total Assets	2,058	2,417
Level 2 [Member]
Total Assets	2,462	2,299
Level 3 [Member]
Total Assets	322	185
Level 3 [Member] | Partnership Interest [Member]
Total Assets	127	108
U S Government Securities [Member]
Total Assets	211	138
U S Government Securities [Member] | Level 2 [Member]
Total Assets	211	138
Government Bonds-Foreign [Member]
Total Assets	39	35
Government Bonds-Foreign [Member] | Level 2 [Member]
Total Assets	38	34
Government Bonds-Foreign [Member] | Level 3 [Member]
Total Assets	1	1
Asset Backed Securities [Member]
Total Assets	4	9
Asset Backed Securities [Member] | Level 2 [Member]
Total Assets	3	8
Asset Backed Securities [Member] | Level 3 [Member]
Total Assets	1	1
Real Estate Investment [Member]
Total Assets	152	66
Real Estate Investment [Member] | Level 3 [Member]
Total Assets	152	66
Short Term Investments [Member]
Total Assets	328	484
Short Term Investments [Member] | Level 1 [Member]
Total Assets	276	469
Short Term Investments [Member] | Level 2 [Member]
Total Assets	52	15
Government And Commercial Mortgage Backed Securities [Member]
Total Assets	8	8
Government And Commercial Mortgage Backed Securities [Member] | Level 2 [Member]
Total Assets	8	8
Guaranteed Investment Contracts [Member]
Total Assets	39	38
Guaranteed Investment Contracts [Member] | Level 3 [Member]
Total Assets	39	38
Corporate Bond Securities [Member]
Total Assets	1,237	1,062
Corporate Bond Securities [Member] | Level 1 [Member]
Total Assets		11
Corporate Bond Securities [Member] | Level 2 [Member]
Total Assets	1,236	1,040
Corporate Bond Securities [Member] | Level 3 [Member]
Total Assets	1	11
Cash And Cash Equivalents [Member]
Total Assets	7	2
Cash And Cash Equivalents [Member] | Level 1 [Member]
Total Assets	7	2
Equity Securities [Member]
Total Assets	2,568	2,978
Equity Securities [Member] | Level 1 [Member]
Total Assets	1,745	2,019
Equity Securities [Member] | Level 2 [Member]
Total Assets	823	959
Hedge Funds [Member]
Total Assets	89	94
Hedge Funds [Member] | Level 2 [Member]
Total Assets	89	94
Other Investments [Member]
Total Assets	33	(121)
Other Investments [Member] | Level 1 [Member]
Total Assets	30	(84)
Other Investments [Member] | Level 2 [Member]
Total Assets	2	3
Other Investments [Member] | Level 3 [Member]
Total Assets	1	(40)
Veba I [Member]
Total Assets	53
Veba I [Member] | Level 2 [Member]
Total Assets	53
Veba I [Member] | Cash And Cash Equivalents [Member]
Total Assets	26
Veba I [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Total Assets	26
Veba I [Member] | Equity Securities [Member]
Total Assets	11
Veba I [Member] | Equity Securities [Member] | Level 2 [Member]
Total Assets	11
Veba I [Member] | Debt Securities [Member]
Total Assets	16
Veba I [Member] | Debt Securities [Member] | Level 2 [Member]
Total Assets	16
V.E.B.A I And II [Member]
Total Assets		59
V.E.B.A I And II [Member] | Level 1 [Member]
Total Assets
V.E.B.A I And II [Member] | Level 2 [Member]
Total Assets		59
V.E.B.A I And II [Member] | Level 3 [Member]
Total Assets
V.E.B.A I And II [Member] | Cash And Cash Equivalents [Member]
Total Assets		30
V.E.B.A I And II [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member]
Total Assets
V.E.B.A I And II [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Total Assets		30
V.E.B.A I And II [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member]
Total Assets
V.E.B.A I And II [Member] | Equity Securities [Member]
Total Assets		12
V.E.B.A I And II [Member] | Equity Securities [Member] | Level 1 [Member]
Total Assets
V.E.B.A I And II [Member] | Equity Securities [Member] | Level 2 [Member]
Total Assets		12
V.E.B.A I And II [Member] | Equity Securities [Member] | Level 3 [Member]
Total Assets
V.E.B.A I And II [Member] | Debt Securities [Member]
Total Assets		17
V.E.B.A I And II [Member] | Debt Securities [Member] | Level 1 [Member]
Total Assets
V.E.B.A I And II [Member] | Debt Securities [Member] | Level 2 [Member]
Total Assets		17
V.E.B.A I And II [Member] | Debt Securities [Member] | Level 3 [Member]
Total Assets