Hi Tim – I hope you’re well. Extensions are created by a company when they’re unable to find an appropriate element in the base taxonomy for their filing that is approved and supported by US SEC.
In the XBRL API, you can use concept.is-base=false
as a filter on the /fact
endpoint to return facts in a company filing that are extensions. For example, here’s a summary of non-dimensionalized elements Apple created for a filing a couple of years ago (returning concept.namespace so you can see these are extensions):
/fact/search?dts.id=306447&concept.is-base=false
&fact.has-dimensions=false&fact.ultimus=true
&fields=fact.value,concept.local-name,
period.fiscal-year.sort(DESC),period.fiscal-period,
concept.namespace