I put together some example dimensional-type queries using the functionality of SECXBRL.info. You can see and walk through the queries here, or if you want you can download this Excel spreadsheet which executes the queries and populates the Excel spreadsheet with the query results.
While Query 5 which shows a breakdown of assets by business segments is the sexiest example (see the results below), by working through all the examples you can start to see some issues you need to keep in mind when querying information across reporting entities.
I am not going to go into any more detail, you can fiddle with the examples on your own (all run on the DOW 30 so you don't need a subscription to the service).
One thing I will point out is how you can manage the reality that some filers have a dimension (or [Axis] they are also called), some do not, and sometimes different dimension-defaults are used by different filers. Walk through the examples and you can see how you can manage all of that using the query.