Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares received for each RSU upon vesting (in shares)	1
Shares reserved for issuance under long-term incentive plans (in shares)	11,000,000
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 34.36	$ 38.34	$ 26.83
Aggregate intrinsic value of options exercised	$ 127	$ 33	$ 132
Cash receipts from exercise of options	85	22	84
Total fair value of vested stock option awards	17	15	13
Total fair value of vested restricted stock unit awards	$ 20	$ 19	$ 19
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period	10 years
Total unrecognized compensation cost related to unvested awards	$ 10
Weighted-average period to recognize total unrecognized compensation cost	2 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested awards	$ 29
Weighted-average period to recognize total unrecognized compensation cost	1 year 9 months 18 days
Periodic Vesting \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Cliff Vesting \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Cliff Vesting \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years

Number of shares for each vested RSU or PRSU award.

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Share based compensation arrangement by share based payment award equity instruments stock options vested in period fair value.

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- Definition

Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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