The Federal Energy Regulatory Commission published their XBRL taxonomy yesterday. You can get to it here. It is a good taxonomy. You can download it via the YETI XBRL taxonomy tool. I downloaded FORM No. 1, validated it successfully with two high-quality XBRL validators. I generated this HTML rendering of FORM No. 1 from the XBRL taxonomy.
I would point out the readability of the taxonomy and the excellent use of hypercubes.