Stock Incentive Plan - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares from treasury stock utilized by the Plan	15	6	132	92
Restricted Stock Units And Performance Stock Units
Share Based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation cost	$ 3	$ 3	$ 10	$ 7

Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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