Contingencies and Commitments (Details) (USD $)	3 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Environmental Contingencies
Liability recorded for projected environmental remediation costs	$ 24,000,000
Guarantees Letters Of Credit [Abstract]
The range of expiration dates of guarantees made by the Parent Company	less than
Contingent Contractual Obligations [Line Items]
Amount	789,000,000
Number of Agreements	36
Commitments to invest in subsidiaries, excluding letters of credit	9,000,000
Litigation Contingencies
Aggregate reserves for claims deemed both probable and reasonably estimable	334,000,000	363,000,000
Loss Contingency Range Of Possible Loss Minimum	230,000,000
Loss Contingency Range Of Possible Loss Maximum	1,500,000,000
Guarantees
Contingent Contractual Obligations [Line Items]
Amount	550,000,000
Number of Agreements	19
Maximum Exposure Range for Each Agreement	<$1 - $222 <$1 - $222
Letters of credit under secured credit facility
Contingent Contractual Obligations [Line Items]
Amount	5,000,000
Number of Agreements	9
Maximum Exposure Range for Each Agreement	<$1 - $2 <$1 - $2
Cash Collateralized Letters Of Credit [Member]
Contingent Contractual Obligations [Line Items]
Amount	$ 234,000,000
Number of Agreements	8
Maximum Exposure Range for Each Agreement	<$1 - $209 <$1 - $209