Bank segment - Contractual Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Available-for-sale
Due in one year or less	$ 370
Due after one year through five years	42,557
Due after five years through ten years	13,934
Due after ten years	0
Total amortized cost	56,861
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,203,271
Amortized cost	1,260,132
Held-to-maturity
Due in one year or less	0
Due after one year through five years	39,858
Due after five years through ten years	20,077
Due after ten years	0
Total amortized cost	59,935
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,099,294
Held-to-maturity investment securities, at amortized cost	1,159,229	$ 1,201,314
Available-for-sale
Due in one year or less	364
Due after one year through five years	41,157
Due after five years through ten years	13,935
Due after ten years	0
Total fair value	55,456
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,028,627
Available-for-sale investment securities, at fair value	1,084,083	$ 1,136,439
Held-to-maturity
Due in one year or less	0
Due after one year through five years	36,634
Due after five years through ten years	17,615
Due after ten years	0
Total fair value	54,249
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	1,031,956
Held-to-maturity investment securities	$ 1,086,205