Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 25
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=51819886&loc=SL6014347-161799

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2015	$ 66,759	$ 549	$ 99,258	$ (32,918)	$ (130)
Balance (in shares) at Dec. 31, 2015		53,000,689
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock to consultant	189		189
Issuance of stock to consultant (in shares)		25,000
Stock based compensation expense	3,090		3,090
Stock options exercised	96	$ 1	95
Stock options exercised (in shares)		61,834
Issuance of stock for vested restricted stock units	1	$ 1
Issuance of stock for vested restricted stock units (in shares)		60,918
Recovery from stockholder, net	(36)		(36)
Tax benefit related to stock options	28		28
Cumulative translation adjustment	(1,475)				(1,475)
Net loss	(11,985)			(11,985)
Balance at Dec. 31, 2016	56,667	$ 551	102,624	(44,903)	(1,605)
Balance (in shares) at Dec. 31, 2016		53,148,441
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation expense	3,422		3,422
Stock options exercised	269	$ 2	267
Stock options exercised (in shares)		171,566
Issuance of stock for vested restricted stock units	0	$ 1	(1)
Issuance of stock for vested restricted stock units (in shares)		80,274
Cumulative translation adjustment	(414)				(414)
Net loss	(15,191)			(15,191)
Balance at Dec. 31, 2017	44,753	$ 554	106,312	(60,094)	(2,019)
Balance (in shares) at Dec. 31, 2017		53,400,281
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock to consultant	102		102
Issuance of stock to consultant (in shares)		25,000
Stock based compensation expense	2,066		2,066
Stock options exercised	251	$ 2	249
Stock options exercised (in shares)		239,000
Issuance of stock for vested restricted stock units	0	$ 1	(1)
Issuance of stock for vested restricted stock units (in shares)		109,940
Fair value of conversion feature on Convertible 4.75% Senior Notes	18,658		18,658
Partial extinguishment of equity component of Convertible 3.75% Senior Notes	(10,522)		(10,522)
Cumulative translation adjustment					(631)
Net loss	(36,256)			(36,256)
Balance at Dec. 31, 2018	$ 18,421	$ 557	$ 116,864	$ (96,350)	$ (2,650)
Balance (in shares) at Dec. 31, 2018		53,774,221