XBRL dimensions and extensions

XBRL dimensions qualify a fact with structured detail, such as a segment, product, geography, class, or scenario. An axis states the kind of breakdown, and a member states the selected category. An extension is a filer-defined taxonomy concept or relationship used when the standard taxonomy does not represent the disclosed accounting meaning adequately.

Start with the accounting conclusion and the current FASB GAAP taxonomy. Search for a standard concept that matches the recognition, measurement, period type, and intended meaning. Then determine whether a dimension carries the needed detail. Create an extension only when the standard taxonomy and permitted dimensional structure do not express the disclosure faithfully. Preserve the extension's definition, data type, period type, balance, anchors, labels, and reviewer approval.

Suppose a filer reports revenue for two products. A standard Revenue concept with a Product axis and two members may preserve comparability better than two custom revenue concepts. A custom concept may be justified for a company-specific accounting item, but a custom label alone does not make it distinct.

The SEC EDGAR XBRL Guide governs technical filing expectations. A valid tag cannot repair a wrong accounting policy, value, unit, or period. This concept supports taxonomy selection and review; it does not authorize a filing or replace the disclosure owner's accounting judgment.