How to aggregate and sum the data grouped by some fields

Based on below 2 messages, I need to aggregate the data based on:

  1. granularity (MyHeader.granularity)
  2. myType (MyHeader.myType)
  3. Currency.

{

            "_source": {
                "MyData": {
                    "MyHeader": {
                        "granularity": "Level1",
                        "myType": "YTD",
                        "businessDate": "2018-12-27"
                    },
                    "MyBreakDown": [
                        {
                            "category": null,
                            "Currency": "eur",
                            "MyDetails": [
                                {
                                    "Id": 123,
                                    "myLocalAmount": 100
                                }
                            ]
                        },
                        {
                            "category": null,
                            "Currency": "clf",
                            "MyDetails": [
                                {
                                    "Id": 234,
                                    "myLocalAmount": 130
                                }
                            ]
                        },
                        {
                            "category": null,
                            "Currency": "usd",
                            "MyDetails": [
                                {
                                    "Id": 120,
                                    "myLocalAmount": 250
                                }
                            ]
                        }
                    ]
                }
            }
        },
  	{

            "_source": {
                "MyData": {
                    "MyHeader": {
                        "granularity": "Level1",
                        "myType": "MTD",
                        "businessDate": "2018-12-27"
                    },
                    "MyBreakDown": [
                        {
                            "category": null,
                            "Currency": "eur",
                            "MyDetails": [
                                {
                                    "Id": 123,
                                    "myLocalAmount": 110
                                }
                            ]
                        },
                        {
                            "category": null,
                            "Currency": "clf",
                            "MyDetails": [
                                {
                                    "Id": 234,
                                    "myLocalAmount": 120
                                }
                            ]
                        },
                        {
                            "category": null,
                            "Currency": "usd",
                            "MyDetails": [
                                {
                                    "Id": 120,
                                    "myLocalAmount": 253
                                }
                            ]
                        }
                    ]
                }
            }
        }

Here I can do basic aggregation:

"aggs": {
"by_granularity": {
"terms" : {
"field": "MyHeader.granularity"
},
"aggs": {
"by_myType ": {
"terms": {
"field": "MyHeader.myType"
}
}
}
}
},
"size":0

However, Currency is under the array field and unable to use it.

I need help how to also use currency in aggregations, so it will give me correct data in buckets.

Data is expected something like:

Level1->YTD->eur = 100
Level1->YTD->clf= 130
Level1->YTD->usd = 250

Level1->MTD->eur = 110
Level1->MTD->clf = 120
Level1->MTD->usd = 253