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, 2018	Dec. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	$ 2,296	$ 2,160
Realized and Unrealized Gains (Losses), net	(128)	292
Fair value of plan assets at end of period	1,864	2,296
Pension Benefits [Member] \| Fair Value, Inputs, Level 3 [Member]
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
Pension Benefits [Member] \| Guaranteed Insurance Contracts [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	0	16
Transfers In (Out)		0
Realized and Unrealized Gains (Losses), net		0
Purchases (Sales), net		(16)
Fair value of plan assets at end of period		0
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	335	332
Realized and Unrealized Gains (Losses), net	(5)	29
Fair value of plan assets at end of period	306	335
OPEB [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	49
Fair value of plan assets at end of period	51	49
OPEB [Member] \| Guaranteed Insurance Contracts [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of period	49	47
Transfers In (Out)	0	0
Realized and Unrealized Gains (Losses), net	4	5
Purchases (Sales), net	(2)	(3)
Fair value of plan assets at end of period	$ 51	$ 49

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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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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