The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Subsequent event (Details) - Neos Therapeutics, Inc. 2015 Stock Option and Incentive Plan - shares	Jan. 01, 2020	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2019
Subsequent event
Increase in number of shares reserved and available for issuance		2,483,815	1,449,847
Shares reserved and available for issuance				3,257,599
Subsequent event
Subsequent event
Increase in number of shares reserved and available for issuance	2,486,633
Shares reserved and available for issuance	5,744,232