This Excel spreadsheet has a matrix of the SEC XBRL filers and certain concepts which I would expect to appear in an XBRL instance of a 10-Q or 10-K SEC filing. The spreadsheet is far from perfect, but it can help to see some things.
First, one error that I have in my spreadsheet is that I am looking for a specific period end date, in my case 2009-09-30, the ending date of the quarter. But there is a problem with this: filers don't all have fiscal year ends of December 31. The breakdown of my set of 403 filings is this from a query I created:
--12-31 345
--06-30 10
--12-26 9
--03-31 6
--05-31 6
--01-02 3
--01-03 3
--02-27 3
--07-03 3
--11-30 2
--12-27 2
--09-26 1
--09-27 1
--10-31 1
--01-01 1
--11-27 1
--04-02 1
--03-28 1
--12-25 1
--01-31 1
--12-28 1
--07-02 1
The strange looking fiscal year ends are 52/53 week year ends commonly used by retailers. This makes it harder to get data out of the filings because you cannot look up "all the third quater filings" as XBRL has no way to indicate "this is the third quarter. You have to figure that out.
The other thing which mucks up the data is extensions created by filers and flexibility in the concepts being reported. For example, whereas about 375 filers reported cash as the concept "us-gaap:CashAndCashEquivalentsAtCarryingValue", the rest did not; they used some other concept for cash which is other than what the US GAAP Taxonomy uses.
Is that flexibility a good thing or a bad thing? Well, from my perspective, what I see is that if there is not enough consistency at the high levels of financial reporting, there will be either little hope for compatibility and/or a number of software vendors (such as data aggregators) serving as middlemen to sort the inconsistencies out using software programs. In my view, that would not be a good thing.
I personally think that there should be a "superstructure" into which everything else fits. How much superstructure is what needs to be figured out. This is not about creating a fixed chart of accounts or a form, this is about exactly the opposite. It is about creating enought superstructure so people don't get fed up with the lack of comparability due to the inconsistencies.
Not a lot, things like perhaps:
Then, everything would fit into that superstructure. You could also change the superstructure maybe, but there would be rigid rules for doing so. It is that superstructure and the consistency it offers which enables the ease of use and comparability needed by investors and analysts. Flexibility would still exist.
The data that I see shows that we are actually reasonably close. We do need to figure out the extension process, being more clear on when, where, and how to extend.
Again, the point is not to create a chart of accounts. The point is to avoid a random free-for-all. And actually, I don't see a free-for-all, what I see in the filings I have looked at thus far is a lot of consistency and a few bad apples.