sqlservr.exe consuming 15gb of physical memory

SQL Server 2008 64bit SP4 (Build # 10.0.6000) on Window Server 2008 R2 64bit OS.

When I open Windows Task Manager, I noticed the sqlservr.exe is using 15107836KB (under headingMemory (private working set)). Pretty much consuming all of the maximum server memory (in MB) allocated for that instance.

Should I be concern? Is there anything I should check / look into?

Thanks