Fair Value (Instruments Not Measured at Fair Value) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
ASSETS
Non-Recourse Debt		$ 15,340	$ 14,783
Liabilities [Abstract]
Recourse debt		4,630	4,671
Carrying Amount
ASSETS
Accounts receivable - noncurrent	[1]	163	232
Non-Recourse Debt		15,340	14,783
Liabilities [Abstract]
Recourse debt		4,630	4,671
Fair Value
ASSETS
Accounts receivable - noncurrent	[1]	217	342
Non-Recourse Debt		15,890	15,185
Liabilities [Abstract]
Recourse debt		4,920	4,899
Value added tax		31	24
Fair Value | Level 1
ASSETS
Accounts receivable - noncurrent	[1]	0	0
Non-Recourse Debt		0	0
Liabilities [Abstract]
Recourse debt		0	0
Fair Value | Level 2
ASSETS
Accounts receivable - noncurrent	[1]	6	20
Non-Recourse Debt		13,350	14,140
Liabilities [Abstract]
Recourse debt		4,920	4,899
Fair Value | Level 3
ASSETS
Accounts receivable - noncurrent	[1]	211	322
Non-Recourse Debt		2,540	1,045
Liabilities [Abstract]
Recourse debt		$ 0	$ 0

[1] These amounts primarily relate to amounts due from CAMMESA, the administrator of the wholesale electricity market in Argentina, and are included in Other noncurrent assets in the accompanying Consolidated Balance Sheets. The fair value and carrying amount of these receivables exclude VAT of $31 million and $24 million as of December 31, 2017 and 2016, respectively.