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Stock Option Plans - Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |  |
Shares Under Option, Beginning balance | 7.9 | 8.8
Shares Under Option, Granted | 1.6 | 1.3
Shares Under Option, Exercised | (1.8) | (1.9)
Shares Under Option, Forfeited or canceled | (0.2) | (0.3)
Shares Under Option, Ending balance | 7.5 | 7.9
Shares Under Option, Exercisable at end of year | 1.9 | 2.0
Shares Under Option, Ending unvested and expected to vest | 5.3 | 5.7
Weighted Average Exercise Price, Beginning balance | $ 56.40 | $ 50.16
Weighted Average Exercise Price, Granted | 86.17 | 79.59
Weighted Average Exercise Price, Exercised | 45.80 | 42.91
Weighted Average Exercise Price, Forfeited or canceled | 65.87 | 57.33
Weighted Average Exercise Price, Ending balance | 65.09 | 56.40
Weighted Average Exercise Price, Exercisable at end of year | 47.17 | 45.03
Weighted Average Exercise Price, Ending unvested and expected to vest | $ 70.74 | $ 59.76
Weighted Average Remaining Contractual Term (in years), Ending balance | 3 years 10 months 9 days | 3 years 9 months
Weighted Average Remaining Contractual Term (in years), Exercisable at end of year | 1 year 9 months 29 days | 1 year 9 months 25 days
Weighted Average Remaining Contractual Term (in years), Ending unvested and expected to vest | 4 years 6 months 3 days | 4 years 4 months 9 days
Aggregate Intrinsic Value, Ending Balance | $ 437.9 | $ 308.6
Aggregate Intrinsic Value, Exercisable at end of year | 147.2 | 101.9
Aggregate Intrinsic Value, Ending unvested and expected to vest | $ 278.1 | $ 201.5

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- Definition Share-based Compensation Arrangement by Share-based Payment Award, Options, NonVested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term. + References No definition available. + Details
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + 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 (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. + 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 (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + 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 (c)(1)(iv)(3) -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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- Definition Number of options outstanding, including both vested and non-vested 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable. + 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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 (e)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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