Employee Benefit Plans - Schedule of Share-based Compensation and Related Income Tax Benefits (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Stock-based compensation expense	$ 19	$ 16	$ 38	$ 36
Less: future tax benefit	3	1	7	3
Stock-based compensation expense, net of tax	16	15	31	33
Share-based Payment Arrangement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Stock-based compensation expense	17	12	44	29
Share-based Payment Arrangement \| Directors Compensation
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Stock-based compensation expense	2		2
Cash-based Payment Arrangement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Stock-based compensation expense	$ 2	$ 4	$ (6)	$ 7

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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