Stock-Based Compensation - RSUs and PSUs, Other Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-Based Compensation
Unrecognized compensation cost related to non-vested awards	$ 821	$ 851
RSUs and PSUs
Stock-Based Compensation
Tax benefits realized in connection with vesting and release of awards	$ 117	$ 180	$ 118
Restricted Stock Units
Stock-Based Compensation
Remaining weighted-average contractual term	3 years	3 years	3 years
Fair value of stock units granted	$ 583	$ 484	$ 557
Fair value of stock units vested and released	381	463	323
Unrecognized compensation cost related to non-vested awards	715	763	814
Cash received from employees as a result of vesting and release of awards	$ 0	0	0
Restricted Stock Units \| Minimum
Stock-Based Compensation
Vesting period	1 year
Restricted Stock Units \| Maximum
Stock-Based Compensation
Vesting period	5 years
Performance Share Units
Stock-Based Compensation
Vesting period	3 years
Fair value of stock units granted	$ 118	113	138
Fair value of stock units vested and released	$ 101	$ 51	$ 81

The total fair value of granted units.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Amount of cash inflow from issuance of shares under share-based compensation arrangement. Issuance includes, but is not limited to, exercise of stock options and similar instruments.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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.

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