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Stock-Based Compensation - Relevant Data Used to Determine the Value of Performance Shares (Detail) - Performance Stock Unit Plan [Member] - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Performance Stock Units Issued and Significant Assumptions Used to Estimate Fair Values
Shares granted	13	40	40
Fair value assumptions, risk free interest rate	2.40%	2.40%	1.60%
Fair value assumptions, expected life in years	2 years 9 months 18 days	3 years	3 years
Fair value assumptions, expected volatility	23.50%	22.00%	20.90%
Fair value assumptions, expected volatility of peer companies	26.20%	25.90%	25.60%
Fair value assumptions, correlation coefficient	34.20%	35.90%	37.80%

X

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- References

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

Rate of weighted-average expected volatility for award under share-based payment arrangement.

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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 (f)(2)(ii)
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- Definition

Expected term of 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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-Section 50
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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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Correlation coefficient.

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Share based compensation arrangement by share based payment award fair value assumptions weighted average volatility rate of peer companies.

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