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Share-based Compensation (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 981	$ 990
Proceeds from stock options exercised		$ 269
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld for employee taxes	5,000	1,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 700	$ 700
Total income tax benefit recognized related to restricted stock awards	$ 200	800
Compensation cost recognition weighted average period	2 years 4 months 28 days
Share-based compensation arrangement, fair value of awards vested	$ 2,200	$ 2,800
Shares granted in period	29,000	27,000
Shares vested in period	21,000	21,000
Unrecognized compensation costs	$ 4,700
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service share based compensation nonvested awards total compensation cost not yet recognized	$ 400
Compensation cost recognition weighted average period	2 years 6 months 21 days
Weighted-average remaining contractual life of options outstanding	6 years 10 months 9 days
Aggregate intrinsic value of options outstanding	$ 1,300
Weighted-average remaining contractual life of options exercisable	6 years 6 months
Aggregate intrinsic value of options exercisable	$ 1,300
Intrinsic value of options exercised		$ 1,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognition weighted average period	2 years 4 months 24 days
Share-based compensation arrangement shares to be issued	42,375
Shares vested in period			273,300
Unrecognized compensation costs	$ 3,800
Performance Shares [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation		$ 200
Shares granted in period		210,000
Performance Shares [Member] \| Key Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation		$ 100
Shares granted in period		63,300
Granted in 2019 [Member] \| Performance Shares [Member] \| Certain Key Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 200	$ 100
Shares granted in period	16,637	19,244
Granted in 2020 [Member] \| Performance Shares [Member] \| Certain Key Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted in period	25,738
Granted in 2020 [Member] \| Performance Shares [Member] \| Key Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 100
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares authorized under stock option plans, exercise price range, lower range limit	$ 26.52
Minimum [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares authorized under stock option plans, exercise price range, upper range limit	$ 171.68
Maximum [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Maximum [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period	10 years