XBRL Essentials

XBRL is the international standard for the electronic representation of business reports. At the heart of the XBRL standard is the XBRL 2.1 Specification, originally released in 2003. This specification defines the basic building blocks of facts, instance documents, concepts and taxonomies which are common to all implementations of XBRL.

These are explained in a little more detail below:

Instance document
An instance document is a collection of facts that together make up a business report. At a technical level an instance document is an XML document with a root element of <xbrli:xbrl>.
A fact is an individual piece of information in a report. For example, reporting that profit at Acme Inc. in 2013 was $10m would be a fact. The fact is represented by reporting a value of 10m against a concept representing "Profit", and associating it with contextual information representing the units (dollars), the period (2013), and the entity ("Acme Inc."). At a technical level, facts are represented by elements in an instance document.
A concept is a definition that provides the meaning for a fact. For example, "Profit", "Turnover", and "Assets" would be typical concepts. At a technical level, concepts correspond to element definitions in an XML Schema.
A taxonomy is a collection of of concept definitions. Typically a taxonomy will corresponding to a particular reporting domain. For example, taxonomies exist for many accounting standards such as IFRS, for various regional GAAP standards, as well as for reporting requirements of individual regulators, government agencies and large enterprises. Technically, a taxonomy consists of an XML Schema document containing element definitions, and a collection of XML documents (linkbases) that provide additional information that forms part of the concept definitions.

Much of the power of the XBRL standard comes from the ability to publish reporting requirements in a standard format, known as a taxonomy. Taxonomies allow the publication of reporting requirements in a manner that can be consumed by compliant software. That software, in turn, can use those requirements to, for example, produce reports (instance documents) which meet the stated requirements.

Most XBRL implementations require:

  • The preparation and maintenance of a taxonomy that captures and standardises specific reporting requirements.
  • The publication of that taxonomy so that it can be used by organisations that need to prepare reports that comply with those requirements.
  • The preparation of instance documents by many organisations that need to comply.
  • The validation and, if necessary, correction of those documents by their preparers against the constraints defined by the taxonomy.
  • The transmission by the preparer organisation of the instance document to the relevant recipients.
  • The receipt and validation of each instance document by the organisation (or organisations) interested in the data contained in the reports.
  • The storage, aggregation and analysis of the data contained in the instance documents, as well as the metadata contained in the relevant taxonomy within relevant business intelligence systems by the recipients of the reports.

While very frequently used by regulators, including securities regulators, prudential regulators, tax regulators, and by business registrars around the world, XBRL is also used across government agencies for intra-governmental reporting, by stock exchanges, across large supply chains, as well as within investment banks and analyst firms, and within large and complex enterprises to enhance reporting inside those organisations.

Multi-dimensional data

The XBRL v2.1 specification provides a fixed set of axes against which facts can be reported. These include the concept axis, and a small number of built-in axes such as period and units. Real world data is, however, often multi-dimensional in its nature. For example, an entity might report profit in a number of geographic regions. Whilst it would be possible to model this by defining a separate concept for "profit" in each region in which it is reported, it would clearly be preferable to model "region" as a separate axis, both to avoid a proliferation of concepts, and for ease of analysis.

The XBRL Dimensions 1.0 specification is a modular extension to the XBRL 2.1 specification which enables the reporting of multi-dimensional data in XBRL. The specification makes it possible for taxonomies to define dimensions against which facts can be reported.

The combination of XBRL 2.1 and XBRL Dimensions 1.0 form the foundation of almost all XBRL deployments, and can be considered the core XBRL specifications.


One of the challenges of business reporting is that in many domains, the underlying reporting standards allow considerable flexibility in exactly what is reported, typically based on what is material to the reporting entity. This makes it impossible to create a single taxonomy that enumerates all concepts and dimensions that might be required by all reporting entities.

XBRL has been designed to allow taxonomies to be extended, allowing taxonomies to be tailored to meet specific reporting requirements. For example, international taxonomies may be extended by national regulators or large enterprises. In some cases, particularly for filings by listed companies controlled by securities regulators, individual filers are permitted to provide their own extension taxonomies, in order to accurately model specific reporting needs.