Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) agreement
Guarantees Letters Of Credit [Abstract]
Lower limit of expiration dates of guarantees (less than one year)	1 year
Upper limit of expiration dates of guarantees (more than 19 years)	19 years
Obligations made by the Parent Company associated with non-recourse debt	$ 14
Contingent Contractual Obligations [Line Items]
Amount	$ 490
Number of Agreements | agreement	26
Parent Company
Contingent Contractual Obligations [Line Items]
Letter Of Credit Fee Range Minimum	0.20%
Letter Of Credit Fee Range Maximum	2.50%
Guarantees and commitments
Contingent Contractual Obligations [Line Items]
Amount	$ 369
Number of Agreements | agreement	14
Maximum Exposure Range, Lower Limit (equal to or less than)	$ 1
Maximum exposure range, upper limit	53
Asset sale related indemnities
Contingent Contractual Obligations [Line Items]
Amount	$ 27	[1]
Number of Agreements | agreement	1	[1]
Maximum exposure range, upper limit	$ 27	[1]
Cash collateralized letters of credit
Contingent Contractual Obligations [Line Items]
Amount	$ 32
Number of Agreements | agreement	4
Maximum Exposure Range, Lower Limit (equal to or less than)	$ 1
Maximum exposure range, upper limit	15
Cash collateralized letters of credit | Parent Company
Contingent Contractual Obligations [Line Items]
Amount	$ 32
Letters of credit under the senior secured credit facility
Contingent Contractual Obligations [Line Items]
Number of Agreements | agreement	7
Letters of credit outstanding	$ 62
Maximum Exposure Range, Lower Limit (equal to or less than)	1
Maximum exposure range, upper limit	$ 29

[1] (1) Excludes normal and customary representations and warranties in agreements for the sale of assets (including ownership in associated legal entities) where the associated risk is considered to be nominal.