Hi.
I'm a programmer from Russia with strong skills in Python.
I've read your description and here's my suggestions.
1. The script will use the Requests library to get XBRL files from SEC. It also will use BeautifulSoup library to process the files and extract data fro them. I'm familiar with the following data formats: CSV, TSV, JSON, XML, XLS, YAML. So XBRL format won't be a problem for me.
2. I also suggest to use Postgresql database to store data extracted from the files. I have an average level of knowledge of databases and SQL queries that helps me to create applications that manage and store data. Mostly I worked with PostgresQL, but I'm also familiar with MySQL and SQLite and Mongo.
I usually use SQLAlchemy as ORM to increase speed of development, but I can work with plain SQL queries too.
I'll be happy to answer your questions.
With best regards,
Sergey.