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Share-based Compensation (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended		21 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 1,200		$ 717		$ 3,415	$ 2,352
Compensation cost recognition weighted average period					2 years 1 month 24 days
Share-based compensation, shares authorized under stock option plans, exercise price range, lower range limit					$ 26.52
Share-based compensation, shares authorized under stock option plans, exercise price range, upper range limit					$ 171.68
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value						$ 18.08
Proceeds from stock options exercised					$ 279	$ 220
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld for employee taxes		1,000		3,000	1,000	3,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	723		488		$ 2,200	$ 1,700
Total income tax benefit recognized related to restricted stock awards	249		167		$ 1,500	1,600
Compensation cost recognition weighted average period					2 years 3 days
Award vesting period					5 years
Share-based compensation arrangement, fair value of awards vested					$ 4,100	$ 7,500
Shares vested in period					32,000	86,000
Unrecognized compensation costs	3,300				$ 3,300		$ 3,300
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	600				$ 600		600
Compensation cost recognition weighted average period					2 years 9 months 3 days
Weighted-average remaining contractual life of options outstanding					7 years 4 months 9 days
Aggregate intrinsic value of options outstanding	5,100				$ 5,100		5,100
Weighted-average remaining contractual life of options exercisable					6 years 7 months 2 days
Aggregate intrinsic value of options exercisable	$ 3,300				$ 3,300		$ 3,300
Intrinsic value of options exercised					$ 1,000	$ 1,400
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement shares to be issued	291,080				291,080		291,080
Unrecognized compensation costs	$ 2,100				$ 2,100		$ 2,100
Performance Shares [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	152		152		455	455
Shares vested in period							210,000
Performance Shares [Member] \| Certain Key Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 205				$ 497
Shares vested in period	17,780				17,780
Performance Shares [Member] \| Key Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 77		$ 77		$ 228	$ 229
Shares vested in period	63,300		63,300		63,300	63,300
Minimum [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					3 years
Maximum [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period					10 years