Employee Compensation and Benefit Plans - Stock Options (Details) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Grant-date fair value of share-based incentive compensation awards \| $	$ 163
Predecessor Plans
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding and exercisable, beginning (in shares) \| shares	194,942
Assumed through acquisition (in shares) \| shares	1,635,518
Exercised (in shares) \| shares	(311,587)
Expired/canceled (in shares) \| shares	(3,346)
Outstanding and exercisable, ending (in shares) \| shares	1,515,527
Exercisable (in shares) \| shares	1,509,976
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding and exercisable, beginning (usd per share) \| $ / shares	$ 13.80
Assumed through acquisition (usd per share) \| $ / shares	33.37
Exercised (usd per share) \| $ / shares	46.92
Expired/canceled (usd per share) \| $ / shares	45.99
Outstanding and exercisable, ending (usd per share) \| $ / shares	53.52
Exercisable (usd per share) \| $ / shares	$ 53.64
Weighted Average Remaining Contractual Term (Years), Outstanding	4 years 4 months 24 days	2 years 10 months 24 days
Weighted Average Remaining Contractual Term (Years), Exercisable	4 years 4 months 24 days
Proceeds from exercise of stock options \| $	$ 15	$ 1

Share-based Compensation Arrangement by Share-based Payment Award, Incentive Compensation, Grant Date Fair Value

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Share-based Compensation Arrangement by Share-based Payment Award, Option, Assumed in Acquisition

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Assumed in Acquisition, Weighted Average Exercise Price

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

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Number of options outstanding, including both vested and non-vested options.

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

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, 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 option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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