Stock Incentive Plans - Summary of Activity Related to Stock Options Units (Detail) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options Outstanding and Exercisable
Shares, options outstanding at beginning of year (in shares)	458,354	722,650	892,532
Shares, assumed from acquisitions (in shares)	0	0	207,645
Shares, exercised (in shares)	(183,566)	(253,899)	(255,503)
Shares, forfeited/expired (in shares)	(28,704)	(10,397)	(122,024)
Shares, options outstanding and exercisable at end of year (in shares)	246,084	458,354	722,650
Weighted Average Exercise Price per Share
Weighted average price per share, options outstanding at beginning of year (USD per share)	$ 7.99	$ 7.96	$ 8.95
Weighted average price per share, assumed from acquisition (USD per share)	0	0	8.92
Weighted average price per share, exercised (USD per share)	7.86	7.77	10.21
Weighted average price per share, forfeited/expired (USD per share)	7.65	11.98	12.12
Weighted average price per share, options outstanding and exercisable at end of year (USD per share)	$ 8.14	$ 7.99	$ 7.96

No definition available.

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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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The addition or reduction in the number of reserved shares that could potentially be issued under the option plan attributable to reasons other than grants, exercises, forfeitures, and expirations during the reporting period.

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

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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 price at which grantees could acquire or could have acquired the underlying shares with respect to any other type of change in shares reserved for issuance.

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

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