Basis of Presentation, Business and Summary of Significant Accounting Policies - Secondary Public Offering (Details) - GMS Inc.	Feb. 28, 2017 $ / shares shares
Selling stockholders | Secondary offering
Secondary Public Offering
Shares sold	7,992,500
Price to the public (in dollars per share) | $ / shares	$ 29.25
Selling stockholders | Underwriters over-allotment option
Secondary Public Offering
Shares sold	1,042,500
Affiliates of AEA | Secondary offering
Secondary Public Offering
Shares sold	3,549,302