SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT - CASH FLOWS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net cash used in operating activities	$ 3,447	$ 3,625	$ 2,311
Expenditures for property, plant and equipment	(3,784)	(3,949)	(4,214)
Expenditures for acquisition	9,776	147	1,342
Net cash used in investing activities	(12,557)	(4,700)	(4,835)
Common stock dividends paid	(877)	(755)	(686)
Preferred dividends paid	(89)	0	0
Issuances of mandatory convertible preferred stock, net of $42 in offering costs in 2018	2,258	0	0
Issuances of common stock, net of $41 in offering costs in 2018	2,272	47	51
Repurchases of common stock	(21)	(15)	(56)
Issuances of long-term debt	9,174	4,509	2,951
Payments on long-term debt	(3,510)	(2,800)	(2,057)
Net cash provided by financing activities	9,006	1,007	2,502
Cash and cash equivalents, January 1	288
Cash and cash equivalents, December 31	190	288
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES
Accrued Merger-related transaction costs	0	31	0
Common dividends issued in stock	54	53	53
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash used in operating activities	213	89	(3)
Expenditures for property, plant and equipment	(11)	(11)	(5)
Expenditures for acquisition	(329)	0	0
Capital contributions to investees	(9,457)	0	0
Decrease (increase) in loans to affiliate, net	(1)	0	457
Expenditures for Merger-related costs	0	(12)	0
Net cash used in investing activities	(9,798)	(23)	452
Common stock dividends paid	(877)	(755)	(686)
Preferred dividends paid	(89)	0	0
Issuances of mandatory convertible preferred stock, net of $42 in offering costs in 2018	2,258	0	0
Issuances of common stock, net of $41 in offering costs in 2018	2,272	47	51
Repurchases of common stock	(21)	(15)	(56)
Issuances of long-term debt	4,969	1,595	499
Payments on long-term debt	(500)	(600)	(750)
Increase (decrease) in loans from affiliates, net	1,520	(239)	504
Payments of Debt Issuance Costs	(37)	(7)	(3)
Net cash provided by financing activities	9,495	26	(441)
Increase (decrease) in cash and cash equivalents	(90)	92	8
Cash and cash equivalents, January 1	104	12	4
Cash and cash equivalents, December 31	14	104	12
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES
Accrued Merger-related transaction costs	0	31	0
Preferred dividends declared but not paid	36	0	0
Common dividends issued in stock	54	53	53
Common dividends declared but not paid	245	$ 207	$ 189
Non-controlling interests [Member] | Parent Company [Member]
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES
Offering costs from issuance of mandatory convertible preferred stock	42
Common Stock [Member] | Parent Company [Member]
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES
Offering costs from issuance of common stock	$ 41