Analysis of the details of why the roll forward computations of the cash flow statement shows some very interesting results. Also, the results are very encouraging because they show a very finite and solvable set of issues.
The details of my analysis can be found here. This test is explained on this page, it is item "C" on that list. To quickly summarize, what I did is create an XBRL Formula to test the cash flow roll forward to see what would happen. That formula is "beginning balance of cash + changes in cash = ending balance of cash" per the cash flow statement. I ran this against 403 filings. I expected two "satisfied" results from each filing. If I did not get that expected result, I then went on to find out why.
Here is what I found for the 403 filings:
- 348 filings showed two satisfied formulas, which is what I would have expected
- 15 filings used some other concept than the concept provided by the US GAAP Taxonomy cash flow statement (us-gaap:CashAndCashEquivalentsAtCarryingValue). These included: us-gaap:CashAndDueFromBanks, us-gaap:Cash, us-gaap:CashCashEquivalentsAndShortTermInvestments, us-gaap:CashCashEquivalentsAndShortTermInvestments
- 9 filings put the concept us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents in a different place than the US GAAP Taxonomy in the calcuation (see this blog post)
- 8 filings did something really nasty, a bad practice in my book, but creating distinct concepts for the beginning and ending cash balances, rather than following what the US GAAP Taxonomy does literally hundreds of times which is creating one concept and using context to differentiate the balances at different periods
- 4 filings created custom concept for net changes in cash, replacing the US GAAP Taxonomy concept
- 4 filings changed the computation relating to cash flows relating to discontinued operations
- 3 filings added a concept for cash flows relating to assets held for sale (which probably should be a taxonomy fix)
- 2 filings had tagging errors
- 2 filings added VIE related cash flows (again, this probably should be an adjustment to the US GAAP Taxonomy
- 2 filings created custom concept for cash balance concept
- 1 filing had a zero balance for cash and did not put in a concept that cash balance
- 1 filing had a funky presentation of cash which I would have never anticipated and is different than all other filers
- 1 filing had a rounding error in both their human readable version and their XBRL
- 1 filing had cash classified as a liability because they had a bank overdraft, which was done correctly but I did not anticipate
- 1 filing did not disclose the balances of cash on their cash flow statement; they did have balances on the balance sheet, but a beginning balance which was needed to get two roll forwards was no where to be found
- 1 filing needs additional work, I cannot figure out what is going on, but something is causing the formula to not work correctly
Again, you can see the specific filings here and that page also provides links to the rendering, formula validation report, the XBRL instance, and some other information so you can take a look at these for yourself.
For me, this information yields good insight on how to create and analyse filings as well as how to build taxonomies.