I have created a Sphinx extension that parses both Google style and NumPy style docstrings, and converts them to standard reStructuredText.
To use it, simply install it:
$ pip install sphinxcontrib-napoleon
And enable it in conf.py:
# conf.py
# Add autodoc and napoleon to the extensions list
extensions = ['sphinx.ext.autodoc', 'sphinxcontrib.napoleon']
More documentation on napoleon here.