The Securities and Exchange Commission published its final rule Financial Disclosures about Guarantors and Issuers of Guaranteed Securities and Affiliates Whose Securities Collateralize a Registrant’s Securities.
The rule was adopted largely as initially proposed and gives parent companies the flexibility to provide the Revised Alternative Disclosures inside or outside of the consolidated financial statements which means that XBRL preparation is optional depending on the location of the disclosures. The rule is effective on January 1, 2021. XBRL US submitted a comment letter arguing against the flexibility allowed in the rule because of concerns that this would cause confusion among investors.
Read the XBRL US letter of Dec 3, 2019: https://xbrl.us/wp-content/uploads/2018/12/XBRL-US-Comment-Letter-RE-Guaranteed-Securities-File-Number-S7-19-18.pdf