Bank segment (HEI only) - Available For Sale Investment Securities (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) issue	Dec. 31, 2017 USD ($) issue
Available-for-sale
Total amortized cost	$ 1,421,897	$ 1,421,622
Gross unrealized gains	954	1,231
Gross unrealized losses	(34,318)	(21,655)
Available-for-sale investment securities	$ 1,388,533	$ 1,401,198
Number of issues, less than 12 months \| issue	33	82
Fair value, less than 12 months	$ 178,068	$ 736,772
Gross unrealized losses, less than 12 months	$ (1,907)	$ (7,664)
Number of issues, more than 12 months \| issue	164	85
Fair value, 12 months or longer	$ 1,066,295	$ 522,208
Gross unrealized losses, 12 months or longer	(32,411)	(13,991)
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Debt Securities, Held-to-maturity	141,875	44,515
Gross unrealized gains	1,446	1
Gross unrealized losses	(1,264)	(104)
Held-to-maturity investment securities	$ 142,057	$ 44,412
Number of issues, less than 12 months \| issue	3	2
Fair value, less than 12 months	$ 29,814	$ 35,744
Gross unrealized losses, less than 12 months	$ (400)	$ (104)
Number of issues, more than 12 months \| issue	2	0
Fair value, 12 months or longer	$ 31,505	$ 0
Gross unrealized losses, 12 months or longer	(864)	0
U.S. Treasury and federal agency obligations
Available-for-sale
Total amortized cost	156,694	185,891
Gross unrealized gains	62	438
Gross unrealized losses	(2,407)	(2,031)
Available-for-sale investment securities	$ 154,349	$ 184,298
Number of issues, less than 12 months \| issue	5	15
Fair value, less than 12 months	$ 25,882	$ 83,137
Gross unrealized losses, less than 12 months	$ (208)	$ (825)
Number of issues, more than 12 months \| issue	19	8
Fair value, 12 months or longer	$ 118,405	$ 62,296
Gross unrealized losses, 12 months or longer	(2,199)	(1,206)
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies
Available-for-sale
Total amortized cost	1,192,169	1,220,304
Gross unrealized gains	789	793
Gross unrealized losses	(31,542)	(19,624)
Available-for-sale investment securities	$ 1,161,416	$ 1,201,473
Number of issues, less than 12 months \| issue	22	67
Fair value, less than 12 months	$ 129,011	$ 653,635
Gross unrealized losses, less than 12 months	$ (1,330)	$ (6,839)
Number of issues, more than 12 months \| issue	145	77
Fair value, 12 months or longer	$ 947,890	$ 459,912
Gross unrealized losses, 12 months or longer	(30,212)	(12,785)
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Debt Securities, Held-to-maturity	141,875	44,515
Gross unrealized gains	1,446	1
Gross unrealized losses	(1,264)	(104)
Held-to-maturity investment securities	$ 142,057	$ 44,412
Number of issues, less than 12 months \| issue	3	2
Fair value, less than 12 months	$ 29,814	$ 35,744
Gross unrealized losses, less than 12 months	$ (400)	$ (104)
Number of issues, more than 12 months \| issue	2	0
Fair value, 12 months or longer	$ 31,505	$ 0
Gross unrealized losses, 12 months or longer	(864)	0
Corporate bonds
Available-for-sale
Total amortized cost	49,398
Gross unrealized gains	103
Gross unrealized losses	(369)
Available-for-sale investment securities	$ 49,132
Number of issues, less than 12 months \| issue	6
Fair value, less than 12 months	$ 23,175
Gross unrealized losses, less than 12 months	$ (369)
Number of issues, more than 12 months \| issue	0
Fair value, 12 months or longer	$ 0
Gross unrealized losses, 12 months or longer	0
Mortgage revenue bonds
Available-for-sale
Total amortized cost	23,636	15,427
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale investment securities	$ 23,636	$ 15,427
Number of issues, less than 12 months \| issue	0	0
Fair value, less than 12 months	$ 0	$ 0
Gross unrealized losses, less than 12 months	$ 0	$ 0
Number of issues, more than 12 months \| issue	0	0
Fair value, 12 months or longer	$ 0	$ 0
Gross unrealized losses, 12 months or longer	0	0
American Savings Bank (ASB)
Available-for-sale securities
Payments to acquire new campus project	76,500
Available-for-sale
Available-for-sale investment securities	1,388,533	1,401,198
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Debt Securities, Held-to-maturity	141,875	44,515
Held-to-maturity investment securities	$ 142,057	$ 44,412

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