_type in FieldData

Using Elasticsearch 1.6 and looking at FieldData stats...
Also using docs value when possible...

My Index has about 35,000,000 documents. So clearly the doc values are working as it looks like from below that the fielddata size for the fields is very small. But why is the _type taking up so much ram? The docs don't mention anything about _type being part of the field data.

  "myIndex": {
     "primaries": {
        "fielddata": {
           "memory_size_in_bytes": 30472436,
           "evictions": 0,
           "fields": {
              "field1": {
                 "memory_size_in_bytes": 2392
              "field2": {
                 "memory_size_in_bytes": 3112
              "field3": {
                 "memory_size_in_bytes": 1184
              "_type": {
                 "memory_size_in_bytes": 30465748

Ok looked at the docs a bit regarding _type.

The _type field is indexed.

Can _type be marked a a doc value also?