To implement the `POST /documents` endpoint without blocking the event loop, we need to offload the synchronous and time-consuming `helpers.save_document` call to a separate thread. This can be efficiently achieved using `asyncio.to_thread`, which runs a blocking function in a thread pool and allows the FastAPI event loop to continue processing other requests concurrently.

Here's the complete implementation:

```python
from fastapi import FastAPI
from pydantic import BaseModel
import asyncio

import helpers  # noqa: F401


app = FastAPI()


class DocumentRequest(BaseModel):
    name: str
    text: str


@app.post("/documents", status_code=201)
async def create_document(document: DocumentRequest):
    bytes_saved = await asyncio.to_thread(
        helpers.save_document, document.name, document.text
    )
    return {"bytes": bytes_saved}
```