Stock-Based Compensation Plans (Summary of Stock Option Activity) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Common Shares
Outstanding at beginning of the period (in shares)	68,093	193,447
Granted (in shares)	0	0
Exercised (in shares)	(54,218)	(79,376)
Forfeited or canceled (in shares)	0	(771)
Outstanding at end of the period (in shares)	13,875	113,300
Exercisable (in shares)	13,875	113,300
Weighted Average Strike Price
Outstanding at beginning of period (usd per share)	$ 41.14	$ 41.62
Granted (usd per share)	0	0
Exercised (usd per share)	40.87	42.32
Forfeited or canceled (usd per share)	0	40.87
Outstanding at end of period (usd per share)	42.18	41.13
Exercisable (usd per share)	$ 42.18	$ 41.13
Stock Options Additional Disclosures
Remaining contractual term, outstanding	4 years 8 months 12 days	1 year 4 months 24 days
Remaining contractual term, exercisable	4 years 8 months 12 days	1 year 4 months 24 days
Intrinsic value, outstanding	$ 427	$ 5,869
Intrinsic value, exercisable	$ 427	$ 5,869

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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.

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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.

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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.

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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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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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.

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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.

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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.

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

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