Stock-Based Compensation Plans - Summary of Performance of Share Activity for Annual Awards (Detail) - Performance Shares [Member] - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Target share pay-out	16,716	10,479
Actual share pay-out (paid in following year)	19,401	10,479
Weighted average fair value per share on grant date	$ 223.81	$ 202.04

Share based compensation arrangement by share based payment award equity instruments other than options performance shares actual payout.

No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options performance shares planned payout.

+ References

No definition available.

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- Definition

Per share or unit weighted-average fair value of 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 (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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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.

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