The eXtensible Business Reporting Language (XBRL) is being leveraged world-over by regulators and filers for reporting business and financial information. ‘XBRLization’ of financial data has become mandatory in many countries.
However, XBRL can be interpreted only by machines. XBRL instance document is composed of XBRL and XLink file and requires a rendering engine or an XBRL instance viewer to interpret and present the data in a human-readable format. The rendering of XBRL instance document is regulated mainly by presentation linkbase that determines the relationships and display order of elements.
What is Inline XBRL or iXBRL?
The Inline XBRL (iXBRL) specification on the other hand has been made human-readable. iXBRL has XBRL data embedded in well-formatted HTML or XHTML file. So though being an XBRL document, it is human-readable as the HTML tags are embedded. The basic idea of developing iXBRL is to allow preparers to retain the original view or representation or formatting of the source document, while creating an XBRL document. XHTML representation of the information is what causes the document to be human readable. Inline document being an XHTML file can be viewed in a browser (preferably, Mozilla Firefox Version3.5 or above). It is also machine-readable, as the document is embedded with XBRL tags.
Moreover, we can also generate an XBRL instance document from an inline document using a processor. iXBRL also minimizes the use of company specific presentation linkbase extensions as the XBRL tags are effectively embedded in the HTML/XHTML formatting of the source document.
iXBRL was originally developed by XBRL International (XII) to meet the requirements of HMRC, the regulatory authority for tax collections in the UK. It was built to retain the formatting of the documents being submitted to HMRC to obtain machine-readable XBRL data bundled with the original human-readable formatting. One of the key requirements for the tax inspectors was the ability to see the submission in its original format.
Edit: SEC has introduced iXBRL filing in 2016. Read 'Inline XBRL to Raise the Ante on Data Quality' to know more.
Shortcoming of iXBRL
A major shortcoming of an iXBRL document is that untagged information, though being visible is unavailable in machine-readable format. However, some information which is not part of the source document can still be tagged and be stored as “hidden information” in iXBRL document.