IDOC_ERROR_ILLEGAL_TYPE: The document does not correspond to the associated repository.
This error is very general. I guess, the SAP does not support this IDOC.
Which IDOC are you posting in SAP. Hope you have translated the IDOC into the flat format using transformHierarchyToFlat built in service. There are many threads with this topic. Please refer them for more help.
HTH
BS
#webMethods#Integration-Server-and-ESB#Adapters-and-E-Standards