Financing Activities Financing Activities- Equity Securities (Details) - USD ($) shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 28, 2018
Equity Programs [Line Items]
Issuance of common stock		$ 34	$ 1,167	$ 698
Common Stock [Member]
Equity Programs [Line Items]
Common stock shares issued	[1]	1,674	46,910	26,925
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%
Common stock shares issued		0

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