Period which an employee's right to exercise a plan is no longer contingent on satisfaction of either a service condition, market condition or a performance condition,in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	selb_DefinedContributionPlanEmployersMatchingContributionVestingPeriod
Namespace Prefix:	selb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

401(k) Savings Plan (Details) - 401(k) Plan - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Contribution Plan Disclosure [Line Items]
Vesting period			4 years
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer contribution made	$ 0.1	$ 0.1	$ 0.1	$ 0.1