Share-Based Plans (Summary of Restricted Stock and Stock Option Activity) (Detail)	12 Months Ended
Dec. 31, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted Stock, Granted (in shares)	0
Restricted stock, Outstanding at end of period (in shares)	233,304
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted, Number of Shares	16,045
Options outstanding, at end of period, Number of Shares	420,931
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Options exercised, Number of Shares	59,861
Options, at end of period, Weighted-average Exercise Price (in dollars per share) \| $ / shares	$ 23.35
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock, Outstanding at beginning of period (in shares)	464,831
Restricted Stock, Granted (in shares)	189,894
Restricted stock, Vested restricted stock awards (in shares)	190,199
Restricted stock, Forfeited (in shares)	14,302
Restricted stock, Outstanding at end of period (in shares)	450,224
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 47.48
Restricted stock, Granted (in dollars per share) \| $ / shares	55.40
Restricted stock, Vested restricted stock awards (in dollars per share) \| $ / shares	38.05
Restricted stock, Forfeited (in dollars per share) \| $ / shares	56.26
Restricted stock, at end of period, Weighted-average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 54.53
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock, Outstanding at beginning of period (in shares)	270,044
Restricted Stock, Granted (in shares)	123,514
Restricted stock, Vested restricted stock awards (in shares)	160,254
Restricted stock, Forfeited (in shares)	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 44.34
Restricted stock, Granted (in dollars per share) \| $ / shares	56.14
Restricted stock, Vested restricted stock awards (in dollars per share) \| $ / shares	32.75
Restricted stock, Forfeited (in dollars per share) \| $ / shares	0
Restricted stock, at end of period, Weighted-average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 54.94
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, at beginning of period, Number of Shares	480,792
Options granted, Number of Shares	0
Options forfeited, Number of Shares	59,861
Options outstanding, at end of period, Number of Shares	420,931
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Options exercised, Number of Shares	0
Options, at beginning of period, Weighted-average Exercise Price (in dollars per share) \| $ / shares	$ 21.73
Options granted, Weighted-Average Exercise Price (in dollars per share) \| $ / shares	0
Options exercised, Weighted-Average Exercise Price (in dollars per share) \| $ / shares	0
Options forfeited, Weighted-Average Exercise Price (in dollars per share) \| $ / shares	10.36
Options, at end of period, Weighted-average Exercise Price (in dollars per share) \| $ / shares	$ 23.35

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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).

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The weighted average fair value at grant date for nonvested equity-based awards issued 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).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

For presentations that combine terminations, 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 or that expired.

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- Definition

Weighted average price of options that were either forfeited or expired.

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- Definition

Net number of share options (or share units) granted during the period.

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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=116856206&loc=d3e5070-113901

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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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
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