Stock-based Compensation - Stock Options Fair Value Assumptions (Detail)	9 Months Ended
Sep. 30, 2020 $ / shares
March 2020 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of stock option award	$ 19.63
Expected dividend yield per share	0.00%
Expected life in years	6 years 4 months 24 days
Expected volatility	42.85%
Risk-free interest rate	0.87%
Grant date fair value per share of option awards	$ 8.42
March 2019 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of stock option award	$ 26.63
Expected dividend yield per share	0.00%
Expected life in years	6 years 1 month 20 days
Expected volatility	39.44%
Risk-free interest rate	2.53%
Grant date fair value per share of option awards	$ 11.29
March 2018 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of stock option award	$ 41.60
Expected dividend yield per share	0.00%
Expected life in years	5 years 8 months 23 days
Expected volatility	37.05%
Risk-free interest rate	2.67%
Grant date fair value per share of option awards	$ 16.38
March 2017 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of stock option award	$ 44.10
Expected dividend yield per share	0.00%
Expected life in years	5 years 9 months 7 days
Expected volatility	39.70%
Risk-free interest rate	2.13%
Grant date fair value per share of option awards	$ 17.90

Agreed-upon price for the exchange of the underlying asset relating to the share-based payment award.

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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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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- 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.

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No definition available.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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

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)(i)
-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 S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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