Condensed Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2018	$ 268,491	$ 13	$ 177,683	$ 90,795
Balance, shares at Dec. 31, 2018		13,126
Issuance of shares of common stock under restricted stock award agreements, shares		64
Forfeiture of shares of common stock under restricted stock award agreements, shares		(4)
Stock-based compensation	4,186		4,186
Shares issued for exercise of stock options	2,077		2,077
Shares issued for exercise of stock options, shares		73
Shares issued in Public Offering, net of offering costs	172,945	$ 2	172,943
Shares issued in public offering, net of offering costs, shares		2,300
Net income	14,500			14,500
Balance at Sep. 30, 2019	462,199	$ 15	356,889	105,295
Balance, shares at Sep. 30, 2019		15,559
Balance at Jun. 30, 2019	281,507	$ 13	181,111	100,383
Balance, shares at Jun. 30, 2019		13,219
Issuance of shares of common stock under restricted stock award agreements, shares		1
Forfeiture of shares of common stock under restricted stock award agreements, shares		(4)
Stock-based compensation	1,470		1,470
Shares issued for exercise of stock options	1,365		1,365
Shares issued for exercise of stock options, shares		43
Shares issued in Public Offering, net of offering costs	172,945	$ 2	172,943
Shares issued in public offering, net of offering costs, shares		2,300
Net income	4,912			4,912
Balance at Sep. 30, 2019	462,199	$ 15	356,889	105,295
Balance, shares at Sep. 30, 2019		15,559
Balance at Dec. 31, 2019	475,592	$ 15	359,545	116,032
Balance, shares at Dec. 31, 2019		15,617
Issuance of shares of common stock under restricted stock award agreements, shares		81
Forfeiture of shares of common stock under restricted stock award agreements, shares		(6)
Stock-based compensation	3,987		3,987
Shares issued for exercise of stock options	3,337	$ 1	3,336
Shares issued for exercise of stock options, shares		109
Net income	24,684			24,684
Balance at Sep. 30, 2020	507,600	$ 16	366,868	140,716
Balance, shares at Sep. 30, 2020		15,801
Balance at Jun. 30, 2020	494,861	$ 16	363,248	131,597
Balance, shares at Jun. 30, 2020		15,665
Issuance of shares of common stock under restricted stock award agreements, shares		81
Stock-based compensation	1,462		1,462
Shares issued for exercise of stock options	2,158		2,158
Shares issued for exercise of stock options, shares		55
Net income	9,119			9,119
Balance at Sep. 30, 2020	$ 507,600	$ 16	$ 366,868	$ 140,716
Balance, shares at Sep. 30, 2020		15,801