Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2014	$ 43,999		$ 323	$ 61,505	$ (17,829)
Balance (in shares) at Dec. 31, 2014			32,312,276
Issuance of common stock upon exercise of stock options and warrants	460		$ 5	455	0
Issuance of common stock upon exercise of stock options and warrants (in shares)			482,506
Issuance of common stock for services	30		$ 0	30	0
Issuance of common stock for services (in shares)			9,835
Value of share-based arrangements	173		$ 0	173	0
Value of share-based arrangements (in shares)			0
Net income	4,763		$ 0	0	4,763
Balance at Dec. 31, 2015	49,425		$ 328	62,163	(13,066)
Balance (in shares) at Dec. 31, 2015			32,804,617
Sale of common stock	48,356		$ 74	48,282	0
Sale of common stock (in shares)			7,392,856
Issuance of common stock upon exercise of stock options and warrants	2,704		$ 13	2,691	0
Issuance of common stock upon exercise of stock options and warrants (in shares)			1,251,199
Excess tax benefits from exercise of stock options	189		$ 0	189	0
Issuance of common stock for services	105		$ 0	105	0
Issuance of common stock for services (in shares)			17,148
Value of share-based arrangements	601		$ 0	601	0
Value of share-based arrangements (in shares)			0
Net income	10,637	[1]	$ 0	0	10,637
Balance at Dec. 31, 2016	112,017		$ 415	114,032	(2,430)
Balance (in shares) at Dec. 31, 2016			41,465,820
Issuance of common stock upon exercise of stock options and warrants	807		$ 12	795	0
Issuance of common stock upon exercise of stock options and warrants (in shares)			1,207,729
Tax withholdings related to net share settlements of stock option awards	(2,026)		$ (3)	(2,023)	0
Tax withholdings related to net share settlements of stock option awards (in shares)			(281,645)
Issuance of common stock for services	47		$ 0	47	0
Issuance of common stock for services (in shares)			6,236
Value of share-based arrangements	1,451		$ 0	1,451	0
Value of share-based arrangements (in shares)			0
Net income	11,157	[1]	$ 0	0	11,157
Balance at Dec. 31, 2017	$ 123,453		$ 424	$ 114,302	$ 8,727
Balance (in shares) at Dec. 31, 2017			42,398,140

[1] The sum of the net earnings per share may not add up to the full year amount due to rounding and because the quarterly calculations are based on varying numbers of shares outstanding.