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XBRL: A Word about Definitions

February 13, 2012

The Edgar filer manual addresses the priority of element attributes to consider when selecting element to tag to the facts in your SEC filing. However, it is important to note that the element attributes that are less important to element selection are essential for other tagging decisions. For example, the balance type for monetary elements is not important when making element selection and mapping decisions. Conversely, the balance type is essential to consider when deciding the appropriateness of applying negated labels.

According to the SEC’s Edgar Filer Manual (EFM) 6.6.29: “When choosing the most appropriate element for facts in one or more periods, the element’s xbrli:periodType attribute takes precedence over the type attribute, which takes precedence over the element’s documentation string…”. The element’s “definition”, or documentation string as it is more properly called, may be listed third, but it is the single most important attribute for communicating the meaning of the amounts being reported. This thought is validated in EFM 6.6.24 which says “The definition is an element’s most important attribute and must be consistent with the financial concept reported”.

After confirming that an element’s period type (duration versus instant) and type (dollars, shares, per share, etc.) attributes are appropriate to use for a line item of facts, the SEC’s Edgar Filer Manual specifies that decisions on the appropriateness of documentation strings should be based on three factors as follows.

Factor 1

EFM 6.6.24 says “If an element used in numeric facts representing amounts in one or more periods has a definition, then the scope of that definition must include the material amounts reported for that line item in the corresponding official HTML/ASCII document.” Generally, an element “has a definition” if there is text defining the element in the documentation string. The documentation string must do more than “fit” what it is being tagged; it must conceptually include all of the material amounts that the related facts consist of. If any of the facts being tagged includes a single material amount that is not within the scope of the documentation string, then the element does not meet this requirement and should not be used.

Factor 2

According to EFM 6.6.25 “An element must not be used in numeric facts representing amounts of a line item in different periods if it has a definition that explicitly excludes one or more of the material amounts in the corresponding official HTML/ASCII document.” This factor covers the opposite side of the materiality question from EFM 6.6.24 above, so if the documentation string excludes even a single material concept that is within one of the facts within an amount on a line item, the element must not be used.

Factor 3

When there is a choice among different elements that have definitions consistent with a set of facts in one or more periods, use the element with the narrowest definition (EFM 6.6.26). Sometime two elements have documentation strings that could work with a single line item attribute. When this happens the Edgar Filer Manual specifies that the element with the narrowest documentation string is the one that should be used.


When selecting elements to map and tag to your SEC filing, remember to think beyond the element’s label, name and balance type. For better element selections first consider the period type and type attributes then verify that the definition (i) includes all the material amounts, (ii) does not exclude any material amounts and (iii) is the narrowest definition that also meets the two materiality tests.

What processes have you implemented to ensure that these and other XBRL best practices are followed?

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