CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Ordinary shares	Preferred shares	Additional paid-in capital	Additional paid-in capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive (loss) income	Treasury shares
Beginning balance (in shares) at Dec. 31, 2019			42,927	0						5,407
Beginning balance at Dec. 31, 2019	$ (29,199)		$ 429	$ 0	$ 434,391		$ (391,215)		$ (22,806)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(865)						(865)
Other comprehensive income (loss)	(821)								(821)
Exercise of stock options (in shares)			146
Exercise of stock options	1,389		$ 2		1,387
Vesting of restricted shares (in shares)			19
Vesting of restricted shares	0
Employee share purchase plan share issuance (in shares)			40
Employee share purchase plan share issuance	88				88
Stock-based compensation expense	742				742
February 2020 private placement (in shares)			8,680	488
February 2020 private placement	60,733		$ 87	$ 5	60,641
Ending balance (in shares) at Mar. 31, 2020			51,812	488						5,407
Ending balance at Mar. 31, 2020	32,067		$ 518	$ 5	497,249		(392,080)		(23,627)	$ (49,998)
Beginning balance (in shares) at Dec. 31, 2019			42,927	0						5,407
Beginning balance at Dec. 31, 2019	$ (29,199)		$ 429	$ 0	434,391		(391,215)		(22,806)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	avdl:AccountingStandardsUpdate202006Member
Ending balance (in shares) at Dec. 31, 2020			58,396	488
Ending balance at Dec. 31, 2020	$ 162,266	$ (12,939)	$ 583	$ 5	566,916	$ (26,699)	(384,187)	$ 13,760	(21,051)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(13,445)						(13,445)
Other comprehensive income (loss)	(1,255)								(1,255)
Exercise of stock options (in shares)			23
Exercise of stock options	106				106
Vesting of restricted shares (in shares)			61
Vesting of restricted shares	0		$ 1		(1)
Employee share purchase plan share issuance (in shares)			8
Employee share purchase plan share issuance	43				43
Stock-based compensation expense	1,728				1,728
Ending balance (in shares) at Mar. 31, 2021			58,488	488
Ending balance at Mar. 31, 2021	$ 136,504		$ 584	$ 5	$ 542,093		$ (383,872)		$ (22,306)