In a large number of cases, a class of stock member is being used on the StatementEquityComponentsAxis. The StatementEquityComponentsAxis represents the components of stockholders’ equity and should not include classes of stock. Classes of stock should be identified on the StatementClassOfStockAxis.
If a company has common stock and the common stock is comprised of two classes, then the value of the common stock for the class should be dimensionalized with the StatementClassOfStockAxis and a Class of Stock Member (Class A for example) and the StatementEquityComponentsAxis with the Common Stock Member. Two axes are used because the class of stock may also have an APIC component or treasury stock component. By using the Class of Stock Member on the Equity Component axis, there is no way to determine if the member represents the par value component, the APIC component or the treasury stock component. In the example below, Common Stock A has common stock par value of $155,100,000 and an additional paid-in capital (APIC) value of $484,000,000. To distinguish these values, the class of stock needs to be on the Class of Stock axis and not the Equity Component axis.
Figure 15. Class of Stock Axis