Employee Benefits - Changes in PBO Related to Pension Plans (Details) - Pension Plan [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
PBO/APBO at beginning of year	$ 1,323	$ 1,338
Interest cost	41	48	$ 44
Actuarial losses (gains)	(66)	37
Benefit payments	(97)	(100)
PBO/APBO at end of year	$ 1,201	$ 1,323	$ 1,338

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

+ Details

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- Definition

Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

+ References

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