Bank segment - Contractual maturities of investment securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Available-for-sale
Due in one year or less	$ 15,821
Due after one year through five years	81,524
Due after five years through ten years	71,775
Due after ten years	0
Total amortized cost	169,120
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	2,660,506
Amortized cost	2,829,626
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	59,877
Due after ten years	0
Total amortized cost	59,877
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	457,273
Amortized cost	517,150
Available-for-sale
Due in one year or less	15,890
Due after one year through five years	79,931
Due after five years through ten years	68,800
Due after ten years	0
Total fair value	164,621
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	2,456,754
Total available-for-sale securities	2,621,375		$ 2,574,618
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	56,046
Due after ten years	0
Total fair value	56,046
Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies	410,190
Total held-to-maturity securities	466,236
Proceeds, gross gains and losses from sales of available-for-sale securities
Proceeds	0	$ 197,354
Gross gains	0	974
Gross losses	0	446
Tax expense on realized gains	$ 0	$ 142