CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance (in shares) at Dec. 31, 2015		19,179,000
Balance at Dec. 31, 2015	$ 118,738	$ 96	$ 139,534	$ (352)	$ (20,540)
Stockholders' Equity [Roll Forward]
Issuance of shares under stock plans, net of shares withheld for tax payments (in shares)		20,000
Issuance of shares under stock plans, net of shares withheld for tax payments	172	$ 0	172
Stock-based compensation, net of shares withheld for tax payments (in shares)		62,000
Stock-based compensation, net of shares withheld for tax payments	1,087	$ 0	1,087
Stock-based compensation, net of shares withheld for tax payments	0		0
Unrealized gains on derivative financial instruments, net of tax	90			90
Tax payments related to stock-based awards	106		(106)
Net income (loss)	(320)
Balance (in shares) at Dec. 31, 2016		19,261,000
Balance at Dec. 31, 2016	119,661	$ 96	140,687	(262)	(20,860)
Stockholders' Equity [Roll Forward]
Issuance of shares under stock plans, net of shares withheld for tax payments (in shares)		25,000
Issuance of shares under stock plans, net of shares withheld for tax payments	219	$ 0	219
Stock-based compensation, net of shares withheld for tax payments (in shares)		24,000
Stock-based compensation, net of shares withheld for tax payments		$ 0	1,317
Unrealized gains on derivative financial instruments, net of tax	98			98
Tax payments related to stock-based awards	27		(27)
Net income (loss)	$ 9,523
Balance (in shares) at Dec. 31, 2017	19,309,829	19,310,000
Balance at Dec. 31, 2017	$ 130,791	$ 96	142,196	(164)	(11,337)
Stockholders' Equity [Roll Forward]
Issuance of shares under stock plans, net of shares withheld for tax payments (in shares)		42,000
Issuance of shares under stock plans, net of shares withheld for tax payments	427	$ 0	427
Stock-based compensation, net of shares withheld for tax payments (in shares)		31,000
Stock-based compensation, net of shares withheld for tax payments		$ 0	1,482
Unrealized gains on derivative financial instruments, net of tax	78
Tax payments related to stock-based awards	92		(92)
Net income (loss)	$ 4,142
Balance (in shares) at Dec. 31, 2018	19,382,641	19,383,000
Balance at Dec. 31, 2018	$ 136,435	$ 97	$ 144,013	$ (86)	$ (7,589)