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Stock Incentive Plan - Additional Information (Details) - USD ($) | 12 Months Ended
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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 |  |

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- Definition 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) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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- Definition 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 Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition 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. + References No definition available. + Details
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- Definition 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 Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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