Contingencies and Commitments (Details) (USD $)	3 Months Ended
	Jun. 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 one year to more than 14 years
Obligations made by the Parent Company associated with non-recourse debt	24,000,000
Contingent Contractual Obligations [Line Items]
Amount	779,000,000
Number of Agreements	38
Commitments to invest in subsidiaries, excluding letters of credit	9,000,000
Litigation Contingencies
Aggregate reserves for claims deemed both probable and reasonably estimable	342,000,000	363,000,000
Loss Contingency Range Of Possible Loss Minimum	227,000,000
Loss Contingency Range Of Possible Loss Maximum	1,400,000,000
Guarantees
Contingent Contractual Obligations [Line Items]
Amount	528,000,000
Number of Agreements	18
Maximum Exposure Range for Each Agreement	<$1 - $219
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
Cash Collateralized Letters Of Credit [Member]
Contingent Contractual Obligations [Line Items]
Amount	$ 246,000,000
Number of Agreements	11
Maximum Exposure Range for Each Agreement	<$1 - $209