Bank segment - Components of investment securities (Details) $ in Thousands	Mar. 31, 2022 USD ($) issue	Dec. 31, 2021 USD ($) issue
Available-for-sale
Available-for-sale investment securities, at fair value	$ 2,621,375	$ 2,574,618
Held-to-maturity
Amortized cost	517,150	522,270
Held-to-maturity investment securities	466,236
American Savings Bank (ASB)
Available-for-sale
Amortized cost	2,829,626	2,618,384
Gross unrealized gains	453	7,969
Gross unrealized losses	(208,704)	(51,735)
Available-for-sale investment securities, at fair value	$ 2,621,375	$ 2,574,618
Gross unrealized losses, Less than 12 months, Number of issues \| issue	184	125
Gross unrealized losses, Less than 12 months, Fair value	$ 1,609,984	$ 1,902,850
Gross unrealized losses, Less than 12 months, Amount	$ (102,135)	$ (38,850)
Gross unrealized losses, 12 months or longer, Number of issues \| issue	64	18
Gross unrealized losses, 12 months or longer, Fair value	$ 904,628	$ 271,012
Gross unrealized losses, 12 months or more, amount	(106,569)	(12,885)
Held-to-maturity
Amortized cost	517,150	522,270
Gross unrealized gains	76	1,648
Gross unrealized losses	(50,990)	(13,444)
Held-to-maturity investment securities	$ 466,236	$ 510,474
Less than 12 months: Number of issues \| issue	26	24
Less than 12 Months: Fair value	$ 303,032	$ 330,477
Less than 12 Months: Amount	$ (27,795)	$ (7,835)
12 months or longer: Number of issues \| issue	13	7
12 months or longer: Fair value	$ 158,370	$ 106,483
12 months or longer: Amount	(23,195)	(5,609)
U.S. Treasury and federal agency obligations \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	109,343	89,714
Gross unrealized gains	75	803
Gross unrealized losses	(3,216)	(427)
Available-for-sale investment securities, at fair value	$ 106,202	$ 90,090
Gross unrealized losses, Less than 12 months, Number of issues \| issue	16	4
Gross unrealized losses, Less than 12 months, Fair value	$ 91,087	$ 44,827
Gross unrealized losses, Less than 12 months, Amount	$ (3,216)	$ (427)
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
Held-to-maturity
Amortized cost	59,877	59,871
Gross unrealized gains	0	168
Gross unrealized losses	(3,831)	(170)
Held-to-maturity investment securities	$ 56,046	$ 59,869
Less than 12 months: Number of issues \| issue	3	2
Less than 12 Months: Fair value	$ 56,046	$ 39,594
Less than 12 Months: Amount	$ (3,831)	$ (170)
12 months or longer: Number of issues \| issue	0	0
12 months or longer: Fair value	$ 0	$ 0
12 months or longer: Amount	0	0
Mortgage-backed securities \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	2,660,506	2,482,618
Gross unrealized gains	277	6,511
Gross unrealized losses	(204,029)	(51,206)
Available-for-sale investment securities, at fair value	$ 2,456,754	$ 2,437,923
Gross unrealized losses, Less than 12 months, Number of issues \| issue	165	120
Gross unrealized losses, Less than 12 months, Fair value	$ 1,484,883	$ 1,845,243
Gross unrealized losses, Less than 12 months, Amount	$ (97,460)	$ (38,321)
Gross unrealized losses, 12 months or longer, Number of issues \| issue	64	18
Gross unrealized losses, 12 months or longer, Fair value	$ 904,628	$ 271,012
Gross unrealized losses, 12 months or more, amount	(106,569)	(12,885)
Held-to-maturity
Amortized cost	457,273	462,399
Gross unrealized gains	76	1,480
Gross unrealized losses	(47,159)	(13,274)
Held-to-maturity investment securities	$ 410,190	$ 450,605
Less than 12 months: Number of issues \| issue	23	22
Less than 12 Months: Fair value	$ 246,986	$ 290,883
Less than 12 Months: Amount	$ (23,964)	$ (7,665)
12 months or longer: Number of issues \| issue	13	7
12 months or longer: Fair value	$ 158,370	$ 106,483
12 months or longer: Amount	(23,195)	(5,609)
Corporate bonds \| American Savings Bank (ASB)
Available-for-sale
Amortized cost	44,481	30,625
Gross unrealized gains	101	655
Gross unrealized losses	(1,459)	(102)
Available-for-sale investment securities, at fair value	$ 43,123	$ 31,178
Gross unrealized losses, Less than 12 months, Number of issues \| issue	3	1
Gross unrealized losses, Less than 12 months, Fair value	$ 34,014	$ 12,780
Gross unrealized losses, Less than 12 months, Amount	$ (1,459)	$ (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	15,296	15,427
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale investment securities, at fair value	$ 15,296	$ 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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