Contingencies and Commitments (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Environmental Contingencies
Liability recorded for projected environmental remediation costs	$ 25,000,000
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	25,000,000
Contingent Contractual Obligations [Line Items]
Amount	618,000,000
Number of Agreements	45
Commitments to invest in subsidiaries, excluding letters of credit	9,000,000
Litigation Contingencies
Aggregate reserves for claims deemed both probable and reasonably estimable	380,000,000	363,000,000
Loss Contingency Range Of Possible Loss Minimum	364,000,000
Loss Contingency Range Of Possible Loss Maximum	1,700,000,000
Guarantees
Contingent Contractual Obligations [Line Items]
Amount	352,000,000
Number of Agreements	21
Maximum Exposure Range for Each Agreement	<$1 - $53
Letters of credit under secured credit facility
Contingent Contractual Obligations [Line Items]
Amount	12,000,000
Number of Agreements	11
Maximum Exposure Range for Each Agreement	<$1 - $7
Cash Collateralized Letters Of Credit [Member]
Contingent Contractual Obligations [Line Items]
Amount	$ 254,000,000
Number of Agreements	13
Maximum Exposure Range for Each Agreement	<$1 - $215