Net Earnings (Loss) Per Share (Details Textual)	Dec. 31, 2012	Dec. 31, 2011
Employee and Director Stock Options And Warrants To Purchase Common Stock	1,415,000	1,432,667

Dilutive securities consisting of employee and director stock options and warrants to purchase entity's common stock.

No definition available.

Name:	alrn_EmployeeAndDirectorStockOptionsToPurchaseCommonStock
Namespace Prefix:	alrn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant