Bank segment - Other Borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Offsetting Liabilities [Line Items]
Other bank borrowings	$ 750,000	$ 695,120
Gross amount  of recognized  liabilities	0	281,000
Gross amount  offset in the  Balance Sheets	0	0
Net amount of liabilities presented in the Balance Sheets	0	281,000
Commercial account holders
Offsetting Liabilities [Line Items]
Net amount of liabilities presented in the Balance Sheets	0	281,000
Financial instruments	0	327,000
Cash collateral pledged	0	0
American Savings Bank (ASB)
Offsetting Liabilities [Line Items]
Advances from the FHLB	200,000	414,000
American Savings Bank (ASB) | Federal Reserve Bank Advances
Offsetting Liabilities [Line Items]
Other bank borrowings	$ 550,000	$ 0