CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital in excess of Par Value	(Accumulated Deficit) Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance (in shares) at Dec. 31, 2017		17,677,000				(1,708,000)
Balance at Dec. 31, 2017	$ 68,986	$ 354	$ 48,349	$ 29,549	$ (3,430)	$ (5,836)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options (in shares)		168,000
Issuance of common stock upon the exercise of stock options	866	$ 3	863
Net issuance of restricted stock awards (in shares)		34,000
Net issuance of restricted stock awards	0
Stock-based compensation	1,039		1,039
Foreign currency translation adjustments	(823)				(823)
Net loss	(24,122)			(24,122)
Balance (in shares) at Dec. 31, 2018		17,879,000				(1,708,000)
Balance at Dec. 31, 2018	45,946	$ 357	50,251	5,427	(4,253)	$ (5,836)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options (in shares)		256,000
Issuance of common stock upon the exercise of stock options	1,433	$ 5	1,428
Net issuance of restricted stock awards (in shares)		225,000
Net issuance of restricted stock awards	0	$ 5	(5)
Issuance of restricted stock for acquisition	27,527		27,527
Treasury stock acquired from employees upon exercise of stock options (in shares)						(23,000)
Treasury stock acquired from employees upon exercise of stock options	(544)					$ (544)
Stock-based compensation	2,706		2,706
Equity component of issued convertible notes	12,465		12,465
Foreign currency translation adjustments	(1,115)				(1,115)
Net loss	$ (15,571)			(15,571)
Balance (in shares) at Dec. 31, 2019	16,629,177	18,360,000				(1,731,000)
Balance at Dec. 31, 2019	$ 72,847	$ 367	94,372	(10,144)	(5,368)	$ (6,380)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options (in shares)	47,000	47,000
Issuance of common stock upon the exercise of stock options	$ 675	$ 1	674
Net issuance of restricted stock awards (in shares)		29,000
Net issuance of restricted stock awards	835	$ 1	834
Net issuance of restricted stock units (in shares)		23,000
Issuance of restricted stock for acquisition (in shares)		908,000
Issuance of restricted stock for acquisition	18	$ 18
Treasury stock acquired from employees upon exercise of stock options (in shares)						(57,000)
Treasury stock acquired from employees upon exercise of stock options	(1,186)		(143)			$ (1,043)
Stock-based compensation	4,251		4,251
Equity component of issued convertible notes	19,060		19,060
Equity component of redeemed 2024 convertible notes (net of deferred taxes of $3.0 million)	(4,372)		(6,808)			$ 2,436
Equity component of redeemed 2024 convertible notes (net of deferred taxes of $1.8 million) (in shares)						722,000
Proceeds from public share offering, net of issuance costs of $0.9 million (in shares)		3,616,000
Proceeds from public share offering, net of issuance costs of $6.0 million)	131,407	$ 72	131,335
Foreign currency translation adjustments	1,432				1,432
Net loss	$ (36,562)			(36,562)
Balance (in shares) at Dec. 31, 2020	21,917,357	22,983,000				(1,066,000)
Balance at Dec. 31, 2020	$ 188,405	$ 459	$ 243,575	$ (46,706)	$ (3,936)	$ (4,987)