Note 12 - Senior Notes and Credit Facilities - Senior Notes and Credit Facilities Balances (Details) (Parentheticals)		6 Months Ended	12 Months Ended
		Apr. 30, 2021	Oct. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Dec. 10, 2019
Senior Unsecured Term Loan Credit Facility Due 2027 [Member]
Debt Instrument, Maturity Date		Feb. 01, 2027	Feb. 01, 2027
The 10.0% 2022 Notes [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		10.00%	10.00%	10.00%	10.00%	10.00%
Debt Instrument, Maturity Date		Jul. 15, 2022	Jul. 15, 2022
The 10.5% 2024 Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		10.50%
The 10.5% 2024 Notes [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		10.50%	10.50%		10.50%	10.50%
Debt Instrument, Maturity Date		Jul. 15, 2024	Jul. 15, 2024
The 10.0% Senior Secured 1.75 Lien Notes due 2025 [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		10.00%	10.00%		10.00%	10.00%
Debt Instrument, Maturity Date		Nov. 15, 2025	Nov. 15, 2025
The 7.75% Senior Secured 1.125 Lien Notes due February 15, 2026 [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		7.75%	7.75%
Debt Instrument, Maturity Date		Feb. 15, 2026	Feb. 15, 2026
The 10.5% Senior Secured 1.25 Lien Notes due February 15, 2026 [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		10.50%	10.50%
Debt Instrument, Maturity Date		Feb. 15, 2026	Feb. 15, 2026
The 11.25% Senior Secured 1.5 Lien Notes due February 15, 2026 [Member]
Debt Instrument, Interest Rate, Stated Percentage		11.25%		11.25%
The 11.25% Senior Secured 1.5 Lien Notes due February 15, 2026 [Member] | Senior Secured Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		11.25%	11.25%
Debt Instrument, Maturity Date		Feb. 15, 2026	Feb. 15, 2026
The 8.0% Senior Notes Due 2027 [Member]
Debt Instrument, Interest Rate, Stated Percentage		8.00%
The 8.0% Senior Notes Due 2027 [Member] | Unsecured Senior Notes Excluding Senior Amortizing Notes and Senior Exchangeable Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage	[1]	8.00%	8.00%
Debt Instrument, Maturity Date	[1]	Nov. 01, 2027	Nov. 01, 2027
The 13.5% Senior Notes Due 2026 [Member]
Debt Instrument, Interest Rate, Stated Percentage		13.50%
The 13.5% Senior Notes Due 2026 [Member] | Unsecured Senior Notes Excluding Senior Amortizing Notes and Senior Exchangeable Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		13.50%	13.50%
Debt Instrument, Maturity Date		Feb. 01, 2026	Feb. 01, 2026
The 5.0% Senior Notes due 2040 [Member]
Debt Instrument, Interest Rate, Stated Percentage		5.00%
The 5.0% Senior Notes due 2040 [Member] | Unsecured Senior Notes Excluding Senior Amortizing Notes and Senior Exchangeable Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		5.00%	5.00%
Debt Instrument, Maturity Date		Feb. 01, 2040	Feb. 01, 2040
The 10.0% Senior Secured 1.75 Lien Term Loans Due 2028 [Member] | Senior Secured Term Loan [Member]
Debt Instrument, Maturity Date		Jan. 31, 2028	Jan. 31, 2028

[1] $26.0 million of 8.0% Senior Notes due 2027 (the "8.0% 2027 Notes") are owned by a wholly-owned consolidated subsidiary of HEI. Therefore, in accordance with GAAP, such notes are not reflected on the Condensed Consolidated Balance Sheets of HEI. On November 1, 2019, the maturity of the 8.0% 2027 Notes was extended to November 1, 2027.