Share-based Compensation and Employee Benefits - Schedule of Changes in Plans’ Assets Included in Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	$ 1,864	$ 2,296
Fair value of plan assets at end of period	2,076	1,864
Pension Benefits \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
OPEB
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	306	335
Fair value of plan assets at end of period	333	306
OPEB \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	51
Fair value of plan assets at end of period	0	51
OPEB \| Guaranteed Insurance Contracts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	51	49
Transfers In (Out)	(49)	0
Realized and Unrealized Gains (Losses), net	0	4
Purchases (Sales), net	(2)	(2)
Fair value of plan assets at end of period	$ 0	$ 51

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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- Definition

Amount, measured using unobservable input, of increase (decrease) in plan asset of defined benefit plan from purchase, sale and settlement of trade associated with underlying investment.

+ References

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

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