Bank segment - Components of investment securities (Details) $ in Thousands	Sep. 30, 2022 USD ($) issue	Dec. 31, 2021 USD ($) issue
Available-for-sale
Amortized cost	$ 2,697,168
Available-for-sale investment securities, at fair value	2,232,336	$ 2,574,618
Held-to-maturity
Amortized cost	510,879	522,270
Held-to-maturity investment securities	411,191
American Savings Bank (ASB)
Available-for-sale
Amortized cost	2,697,168	2,618,384
Gross unrealized gains	13	7,969
Gross unrealized losses	(464,845)	(51,735)
Available-for-sale investment securities, at fair value	$ 2,232,336	$ 2,574,618
Gross unrealized losses, less than 12 months, number of issues \| issue	160	125
Gross unrealized losses, less than 12 months, fair value	$ 853,914	$ 1,902,850
Gross unrealized losses, less than 12 months, amount	$ (120,203)	$ (38,850)
Gross unrealized losses, 12 months or longer, number of issues \| issue	110	18
Gross unrealized losses, 12 months or longer, fair value	$ 1,360,712	$ 271,012
Gross unrealized losses, 12 months or more, amount	(344,642)	(12,885)
Held-to-maturity
Amortized cost	510,879	522,270
Gross unrealized gains	0	1,648
Gross unrealized losses	(99,688)	(13,444)
Held-to-maturity investment securities	$ 411,191	$ 510,474
Less than 12 months, number of issues \| issue	15	24
Less than 12 months, fair value	$ 125,039	$ 330,477
Less than 12 months, amount	$ (25,154)	$ (7,835)
12 months or longer, number of issues \| issue	25	7
12 months or longer: fair value	$ 286,152	$ 106,483
12 months or longer, amount	(74,534)	(5,609)
U.S. Treasury and federal agency obligations \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	104,278	89,714
Gross unrealized gains	0	803
Gross unrealized losses	(7,865)	(427)
Available-for-sale investment securities, at fair value	$ 96,413	$ 90,090
Gross unrealized losses, less than 12 months, number of issues \| issue	16	4
Gross unrealized losses, less than 12 months, fair value	$ 78,651	$ 44,827
Gross unrealized losses, less than 12 months, amount	$ (5,672)	$ (427)
Gross unrealized losses, 12 months or longer, number of issues \| issue	1	0
Gross unrealized losses, 12 months or longer, fair value	$ 17,762	$ 0
Gross unrealized losses, 12 months or more, amount	(2,193)	0
Held-to-maturity
Amortized cost	59,888	59,871
Gross unrealized gains	0	168
Gross unrealized losses	(8,918)	(170)
Held-to-maturity investment securities	$ 50,970	$ 59,869
Less than 12 months, number of issues \| issue	2	2
Less than 12 months, fair value	$ 33,821	$ 39,594
Less than 12 months, amount	$ (6,106)	$ (170)
12 months or longer, number of issues \| issue	1	0
12 months or longer: fair value	$ 17,149	$ 0
12 months or longer, amount	(2,812)	0
Mortgage-backed securities \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	2,533,445	2,482,618
Gross unrealized gains	13	6,511
Gross unrealized losses	(452,503)	(51,206)
Available-for-sale investment securities, at fair value	$ 2,080,955	$ 2,437,923
Gross unrealized losses, less than 12 months, number of issues \| issue	139	120
Gross unrealized losses, less than 12 months, fair value	$ 735,328	$ 1,845,243
Gross unrealized losses, less than 12 months, amount	$ (110,054)	$ (38,321)
Gross unrealized losses, 12 months or longer, number of issues \| issue	109	18
Gross unrealized losses, 12 months or longer, fair value	$ 1,342,950	$ 271,012
Gross unrealized losses, 12 months or more, amount	(342,449)	(12,885)
Held-to-maturity
Amortized cost	450,991	462,399
Gross unrealized gains	0	1,480
Gross unrealized losses	(90,770)	(13,274)
Held-to-maturity investment securities	$ 360,221	$ 450,605
Less than 12 months, number of issues \| issue	13	22
Less than 12 months, fair value	$ 91,218	$ 290,883
Less than 12 months, amount	$ (19,048)	$ (7,665)
12 months or longer, number of issues \| issue	24	7
12 months or longer: fair value	$ 269,003	$ 106,483
12 months or longer, amount	(71,722)	(5,609)
Corporate bonds \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	44,412	30,625
Gross unrealized gains	0	655
Gross unrealized losses	(4,477)	(102)
Available-for-sale investment securities, at fair value	$ 39,935	$ 31,178
Gross unrealized losses, less than 12 months, number of issues \| issue	5	1
Gross unrealized losses, less than 12 months, fair value	$ 39,935	$ 12,780
Gross unrealized losses, less than 12 months, amount	$ (4,477)	$ (102)
Gross unrealized losses, 12 months or longer, number of issues \| issue	0	0
Gross unrealized losses, 12 months or longer, fair value	$ 0	$ 0
Gross unrealized losses, 12 months or more, amount	0	0
Mortgage revenue bonds \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	15,033	15,427
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale investment securities, at fair value	$ 15,033	$ 15,427
Gross unrealized losses, less than 12 months, number of issues \| issue	0	0
Gross unrealized losses, less than 12 months, fair value	$ 0	$ 0
Gross unrealized losses, less than 12 months, amount	$ 0	$ 0
Gross unrealized losses, 12 months or longer, number of issues \| issue	0	0
Gross unrealized losses, 12 months or longer, fair value	$ 0	$ 0
Gross unrealized losses, 12 months or more, amount	$ 0	$ 0

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Held-To-Maturity Securities, More Than 12 Months, Number Of Issues

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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