Stock-Based Compensation - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares available for grant under Company's stock incentive plan (subject to adjustment for forfeitures)	35
Fair value of shares vested	$ 182	$ 180	$ 128
Stock-based compensation expense	174	163	150
Stock-based compensation expense on an after tax basis	130	$ 101	$ 93
Unrecognized compensation cost related to nonvested share-based arrangements granted under plans	$ 171
Unrecognized compensation cost recognized over a weighted-average period as compensation expense	1 year 10 months 24 days
Minimum [Member]
Stock and unit awards vesting period	3 years
Maximum [Member]
Date of grant exercisable period	10 years
Stock and unit awards vesting period	5 years

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
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- Definition

The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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-Publisher FASB
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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Date of grant exercisable period.

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Stock and unit awards vesting period.

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