Yes, it is documented here. However the VS installer is a Windows binary and the offline installer requires you run it so you'll need a Windows machine. You can use any machine you want though, it doesn't have to be a machine on a company network.
On a Windows machine with internet download the bootstrapper for the edition you need to install from the link given above. Then follow the steps to create a local layout (folder structure) containing the workloads you want. After the bootstrapper is done you have the necessary structure that you can burn to a DVD or copy to a USB drive to install on any machine you want.
Note that I don't recommend you install everything in VS as that is a waste of space unless you need it all (C++, C#, game development, web dev, etc). Therefore you should provide the list of workloads to install when building the layout. But this can be a pain as well so I might instead recommend that you take a Windows machine with INet access and run the VS installer to install just the components you care about. Then go back into the installer and there is an option to export the installed configuration. This gives you the template of the components/workloads you need. It is this list of components that you need to pass to the bootstrapper to tell it what things to download. However I don't know if the generated file is in a format that you can use with the bootstrapper.
Yet another approach, if the machines have network access but not INet, is to use a network installation. It is basically the same process except you put it on a network drive to be accessed by clients. That process is documented here.