This study investigates whether XBRL filings of 10Ks and 10Qs possess incremental information content beyond current EDGAR filings in HTML format. The sample comprises of 342 voluntary XBRL filings from the period of 2005 to June 30, 2008. We document a significant market reaction on the day when XBRL reports are filed. The market response is stronger for larger firms, more recent filings and more timely filings. Furthermore, it is more pronounced in instances where multiple reports are filed. Using the R2 in a regression of fiscal quarter abnormal returns on XBRL filing abnormal returns, we find that approximately 1.2% to 8.0% out of total information content in earnings disclosures is associated with these XBRL filings.