xbrli:decimalsType 

This type is used to specify the value of the decimals attribute 
on numeric items.  It consists of the union of integer and "INF" 
(used to signify that a number is expressed to an infinite number 
of decimal places or "exact value").

Simple Type Information

Used By

Attribute xbrli:numericItemAttrs/@decimals

Source 

<simpleType name="decimalsType">
  <annotation>
    <documentation>This type is used to specify the value of the decimals attribute on numeric items. It consists of the union of integer and "INF" (used to signify that a number is expressed to an infinite number of decimal places or "exact value").</documentation>
  </annotation>
  <union memberTypes="integer ">
    <simpleType>
      <restriction base="string">
        <enumeration value="INF"/>
      </restriction>
    </simpleType>
  </union>
</simpleType>