Group Results of terms aggs in "parent" bucket

Hey,

I'm trying to group results which I get after doing the terms aggregation. I'm getting the following results:
hospital 1, doc_count 20; hospital 2, doc_count 32; hospital 3, doc_count 21; facility 1, doc_count 11; facility 2, doc_count 33;
now I would like to summarize these in two buckets: "all_hospitals", doc_count 73 and "all_facilities", doc_count 44 is there any way do this? thank you very much for your answer