Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands		Common Stock [Member]		Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2016		13,373,000
Balance at Dec. 31, 2016		$ 24,547		$ 70,218	$ (659)	$ 94,106
Net income						2,252
Other comprehensive income, net of tax					256	256
Comprehensive income						2,508
Balance at Mar. 31, 2017					(403)
Balance (in shares) at Dec. 31, 2016		13,373,000
Balance at Dec. 31, 2016		$ 24,547		70,218	(659)	94,106
Net income				7,344		7,344
Other comprehensive income, net of tax					393	393
Comprehensive income						7,737
Dividend on common stock				(1,862)		(1,862)
Stock issued pursuant to public offering, net of underwriting discounts and expenses of $1.7 million (in shares)		2,738,000
Stock issued pursuant to public offering, net of underwriting discounts and expenses of $1.7 million		$ 26,778				26,778
Stock compensation grants (in shares)		4,000
Stock compensation grants		$ 41				41
Common stock issued under employee plans (in shares)		30,000
Stock options exercised (in shares)		52,000
Stock options exercised		$ 245				245
Compensation expense associated with stock options		23				23
Compensation expense associated with restricted stock, net of cash paid when directly withholding shares for tax-withholding purposes		$ 196				$ 196
Balance (in shares) at Dec. 31, 2017		16,197,000	[1]			16,271,563
Balance at Dec. 31, 2017	[1]	$ 51,830		75,700	(266)	$ 127,264
Net income				3,241		3,241
Other comprehensive income, net of tax					(2,426)	(2,426)
Comprehensive income						815
Dividend on common stock				(486)		(486)
Stock compensation grants (in shares)		4,000
Stock compensation grants		$ 45				45
Common stock issued under employee plans (in shares)		21,000
Stock options exercised (in shares)		19,000
Stock options exercised		$ 113				113
Compensation expense associated with stock options		3				3
Compensation expense associated with restricted stock, net of cash paid when directly withholding shares for tax-withholding purposes		$ (32)				$ (32)
Reclassification of accumulated other comprehensive income due to tax rate change				52	(52)
Balance (in shares) at Mar. 31, 2018		16,241,000	[1]			16,315,402
Balance at Mar. 31, 2018	[1]	$ 51,959		$ 78,507	$ (2,744)	$ 127,722

[1] Excludes 74 unvested restricted shares