Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 1,217	$ 1,366
Net actuarial losses of defined benefit plans:
Adjustments	(2)	(16)
Recognized within net income	10	9
Prior service credit of defined benefit plans:
Recognized within net income	0	(1)
Other comprehensive income (loss)	8	(8)
Total comprehensive income	$ 1,225	$ 1,358

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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