Bank segment - Contractual maturities of investment securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Available-for-sale
Due in one year or less	$ 2,579
Due after one year through five years	127,548
Due after five years through ten years	14,766
Due after ten years	0
Total amortized cost	144,893
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,500,717
Amortized cost	1,645,610
Held-to-maturity
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	59,900
Due after ten years	0
Total amortized cost	59,900
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,178,285
Amortized cost	1,238,185	$ 1,251,747
Available-for-sale
Due in one year or less	2,531
Due after one year through five years	118,523
Due after five years through ten years	14,766
Due after ten years	0
Total fair value	135,820
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,283,935
Total available-for-sale securities	1,419,755	$ 1,429,667
Held-to-maturity
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	52,728
Due after ten years	0
Total fair value	52,728
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,105,362
Total held-to-maturity securities	$ 1,158,090