Financing Activities Financing Activities- Equity Securities (Details) $ in Millions		1 Months Ended			12 Months Ended
		Nov. 30, 2019 USD ($) shares	Sep. 30, 2018 USD ($) shares	May 31, 2018 counterparties shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Feb. 28, 2018 USD ($)
Equity Programs [Line Items]
Issuance of common stock | $					$ 1,167	$ 698	$ 453
Common Stock [Member]
Equity Programs [Line Items]
Common stock shares issued	[1]				46,910,000	26,925,000	13,667,000
Common Stock [Member] | Forward Sale Agreement [Member]
Equity Programs [Line Items]
Issuance of common stock | $		$ 1,100	$ 520
Common stock shares issued		43,250,000	20,000,000
Total Number Of Shares Issued In Forward Sales Agreements And Overallotment Option				63,250,000
Number of Counterparties | counterparties				2
Forward Contract Indexed to Issuer's Equity, Shares				55,000,000
Over-Allotment Option [Member] | Common Stock [Member] | Forward Sale Agreement [Member]
Equity Programs [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares				8,250,000
At The Market Stock Offering Program [Member]
Equity Programs [Line Items]
Common Stock Aggregate Sales Price | $								$ 1,000
Maximum Percentage Paid To Selling Agents					2.00%
Issuance of common stock | $						$ 119
Common stock shares issued					0	42,000,000

[1] Shares in thousands. Each share entitles the holder to one vote on any question presented at any shareowners' meeting.