Bank segment (HEI only) - Off Balance Sheet Arrangements and Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended
	Sep. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
American Savings Bank (ASB)
Guarantees
Minimum reserve ratio	1.36%
FDIC insurance assessment		$ 2,300	$ 1,200	$ 2,500
Reserve for Off-balance Sheet Activities
Guarantees
Unused commitments to extend credit		1,963,802	1,878,791
Home equity line of credit
Guarantees
Unused commitments to extend credit		1,248,773	1,290,854
Commercial real estate
Guarantees
Unused commitments to extend credit		574,281	484,806
Consumer
Guarantees
Unused commitments to extend credit		69,168	70,088
Residential 1-4 family
Guarantees
Unused commitments to extend credit		57,862	21,131
Commercial and financial standby letters of credit
Guarantees
Unused commitments to extend credit		$ 13,718	$ 11,912