Fair Value (Instruments Not Measured at Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Carrying Amount [Member]
Financial Instruments Not Measured At Fair Value In the Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable - noncurrent	$ 300	[1]	$ 304	[1]
Non-recourse debt	15,399		15,383
Recourse debt	5,671		5,962
Fair Value [Member]
Financial Instruments Not Measured At Fair Value In the Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable - noncurrent	163	[1]	188	[1]
Non-recourse debt	16,394		16,110
Recourse debt	6,032		6,628
Value added tax	52		55
Fair Value [Member] | Level 1 [Member]
Financial Instruments Not Measured At Fair Value In the Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable - noncurrent	0	[1]	0	[1]
Non-recourse debt	0		0
Recourse debt	0		0
Fair Value [Member] | Level 2 [Member]
Financial Instruments Not Measured At Fair Value In the Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable - noncurrent	0	[1]	0	[1]
Non-recourse debt	14,096		13,811
Recourse debt	6,032		6,628
Fair Value [Member] | Level 3 [Member]
Financial Instruments Not Measured At Fair Value In the Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable - noncurrent	163	[1]	188	[1]
Non-recourse debt	2,298		2,299
Recourse debt	$ 0		$ 0

[1] These accounts receivable principally relate to amounts due from the independent system operator in Argentina and are included in “Noncurrent assets — Other” in the accompanying condensed consolidated balance sheets. The fair value of these accounts receivable excludes value-added tax of $52 million and $55 million at June 30, 2013 and December 31, 2012, respectively.