The roles of XBRL and processed XBRL in 10-K readability

The size and composition of the 10-K file have changed dramatically since the mandatory adoption of XBRL. We re-examine 10-K file size as a readability proxy by decomposing 10-K file size into its main components, which include XBRL, processed XBRL (a twin to XBRL that allows XBRL information to be accessed using viewer software) and text. We find that 10-K file size reduces readability before XBRL's adoption in 2012 but enhances readability after adoption and that the XBRL-related components can explain the reversal of this relation. As the XBRL-related components only include financial statement information, our results indicate that more XBRL data improves users' understanding of the financial statements, which is in contrast to the text component of the 10-K where a larger file size is associated with lower readability. As such, our study identifies financial statement readability as a distinct and important dimension of disclosure quality that has been overlooked in the prior literature.