Investments In and Advances To Affiliates - Summarized Financial Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Schedule of Equity Method Investments [Line Items]
Revenue		$ 2,431	$ 2,625	$ 2,483	$ 2,650	$ 2,622	$ 2,837	$ 2,537	$ 2,740	$ 10,189	$ 10,736	$ 10,530
Operating margin		560	701	502	586	646	671	600	656	2,349	2,573	2,465
Net income (loss)		(120)	$ 298	$ 67	$ 233	181	$ 191	$ 416	$ 777	478	1,565	(777)
Assets, Current		5,231				5,015				5,231	5,015
Liabilities, Current		5,096				4,399				5,096	4,399
Liabilities, Noncurrent		22,435				21,639				22,435	21,639
Stockholders' Equity Attributable to Noncontrolling Interest		2,233				2,396				2,233	2,396	2,380	$ 2,461
Stockholders' Equity Attributable to Parent		2,996				3,208				2,996	3,208
Undistributed Earnings Of Minority Owned Affiliates Included In Retained Earnings		14								14
Distributions Received From Minority Owned Affiliates										23	83	69
Basis Difference Between Carrying Amount And Investment		225								225
Minority Owned Affiliates
Schedule of Equity Method Investments [Line Items]
Revenue										1,122	962	762
Operating margin										124	135	165
Net income (loss)										(724)	14	72
Assets, Current		831				558				831	558
Assets, Noncurrent		7,220				5,918				7,220	5,918
Liabilities, Current		1,271				546				1,271	546
Liabilities, Noncurrent		3,966				3,309				3,966	3,309
Stockholders' Equity Attributable to Parent		2,814				2,622				2,814	2,622
Majority Owned Affiliates
Schedule of Equity Method Investments [Line Items]
Revenue										49	40	16
Operating margin										(5)	3	5
Net income (loss)										(7)	(3)	$ (15)
Assets, Current		166				89				166	89
Assets, Noncurrent		982				41				982	41
Liabilities, Current		141				35				141	35
Liabilities, Noncurrent		1,052				122				1,052	122
Stockholders' Equity Attributable to Parent		(45)				$ (27)				(45)	$ (27)
Gas Natural del Este [Member]
Schedule of Equity Method Investments [Line Items]
Noncash or Part Noncash Divestiture, Amount of Consideration Received	$ 55
Fair Value, Inputs, Level 3 [Member] | Long Lived Assets Held For Sale [Member] | OPGC Affiliate [Member]
Schedule of Equity Method Investments [Line Items]
Assets Carrying Amount Disclosure Nonrecurring		$ 212								$ 212