Basis of Presentation - Effects To Statements Of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Income	$ 539	$ 643	$ 590
Depreciation and amortization	987	933	855
Deferred taxes	17	164	148
Current liabilities	160	(2)	99
Net Cash Provided by Operating Activities	1,288	1,588	1,781
Capital expenditures	(2,781)	(2,735)	(1,777)
Net Cash Used in Investing Activities	(2,858)	(2,708)	(1,554)
Cash paid for interest, net of amounts capitalized	$ 278	270	224
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Income		676	598
Depreciation and amortization		934	855
Deferred taxes		138	151
Current liabilities		(5)	98
Net Cash Provided by Operating Activities		1,593	1,791
Capital expenditures		(2,740)	(1,787)
Net Cash Used in Investing Activities		(2,713)	(1,564)
Cash paid for interest, net of amounts capitalized		266	224
Correction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Income		(33)	(8)
Depreciation and amortization		(1)	0
Deferred taxes		26	(3)
Current liabilities		3	1
Net Cash Provided by Operating Activities		(5)	(10)
Capital expenditures		5	10
Net Cash Used in Investing Activities		5	10
Cash paid for interest, net of amounts capitalized		$ 4	$ 0