Stock Incentive Plan - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock plans, term	10 years
Maximum number of shares to be issued in stock incentive plan (in shares)	149,983
Common stock awarded in SI plan (in shares)	0		0
Share-based compensation arrangement by share-based payment award, options, exercises in period, intrinsic value			$ 176,000
Number of anti-dilutive shares not considered in computing aggregate intrinsic value of outstanding shares and exercisable shares	0	0	0
Number of anti-dilutive shares not considered in computing diluted earnings per share	0	0	0
Unrecognized share-based compensation cost	$ 1,156,000,000	$ 1,053,000,000	$ 795,000,000
Stock Unit Awards and Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock awarded in SI plan (in shares)	25,950	26,700	28,700
Annual Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, period of recognition	4 years
Cumulative Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, period of recognition	3 years

Stock incentive plan, term.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
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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.

+ References

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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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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Number of shares authorized for issuance under share-based payment arrangement.

+ References

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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.

+ References

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- Definition

Gross number of share options (or share units) granted during the period.

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