Bank segment (HEI only) - Off Balance Sheet Arrangements and Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
American Savings Bank (ASB)
Guarantees
FDIC insurance assessment	$ 2,600	$ 3,200
American Savings Bank (ASB) | Indemnification Agreement
Guarantees
Accrued indemnification litigation obligation	1,100
Reserve for Off-balance Sheet Activities
Guarantees
Unused Commitments to Extend Credit	1,780,437	1,842,799
Home equity line of credit
Guarantees
Unused Commitments to Extend Credit	1,214,103	1,146,339
Commercial and commercial real estate
Guarantees
Unused Commitments to Extend Credit	466,510	577,410
Consumer
Guarantees
Unused Commitments to Extend Credit	68,053	64,762
Residential 1-4 family
Guarantees
Unused Commitments to Extend Credit	18,635	38,271
Commercial and financial standby letters of credit
Guarantees
Unused Commitments to Extend Credit	$ 13,136	$ 16,017