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Common Stock, Dividend Rate Approved

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The maximum ownership percentage for voting allowed for any one shareholder.

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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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Aggregate number of common shares reserved for future issuance.

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Face amount or stated value per share of common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.

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Amount of stock repurchase plan authorized.

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Number of shares of common and preferred stock retired from treasury during the period.

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Shareholders' equity (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020 SFr / shares shares	Dec. 31, 2019 SFr / shares shares	Dec. 31, 2018 shares	Feb. 01, 2021 USD ($)	Nov. 19, 2020 USD ($)	May 31, 2020 $ / shares	May 20, 2020 $ / shares	Nov. 21, 2019 USD ($)	May 31, 2019 $ / shares	Dec. 01, 2018 USD ($)	May 31, 2018 $ / shares	Dec. 31, 2017 shares	Dec. 21, 2017 USD ($)
Stockholders' Equity Note [Abstract]
Common Stock, Dividend Rate Approved \| $ / shares							$ 0.78		$ 0.75		$ 0.73
The number of votes associated with one Common Share	one
Annual dividend per share approved by shareholders \| $ / shares						$ 3.12			$ 3.00		$ 2.92
Authorized Share Capital [Line Items]
Common Shares, par value \| SFr / shares	SFr 24.15	SFr 24.15
Common Shares, shares issued \| shares	477,605,264	479,783,864	479,783,864									479,783,864
Treasury Stock, Shares, Retired \| shares	2,178,600	0	0
The maximum ownership percentage for voting allowed for any one shareholder	10.00%
General Purpose
Authorized Share Capital [Line Items]
Authorized share capital for future issuance \| shares	200,000,000
Issuance of Debt
Authorized Share Capital [Line Items]
Authorized share capital for future issuance \| shares	33,000,000
Employee Benefit Plans
Authorized Share Capital [Line Items]
Authorized share capital for future issuance \| shares	25,410,929
2018 Stock Repurchase Plan [Member] [Domain]
Authorized Share Capital [Line Items]
Stock repurchase program authorized amount													$ 1,000
2019 Stock Repurchase Plan [Member]
Authorized Share Capital [Line Items]
Stock repurchase program authorized amount										$ 1,500
Nov 2019 Stock Repurchase Plan [Member]
Authorized Share Capital [Line Items]
Stock repurchase program authorized amount								$ 1,500
Nov 2020 Stock Repurchase Plan [Member]
Authorized Share Capital [Line Items]
Stock repurchase program authorized amount					$ 1,500
Subsequent Event [Member] \| Nov 2020 Stock Repurchase Plan [Member]
Authorized Share Capital [Line Items]
Stock repurchase program authorized amount				$ 2,500
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