Equity method investment - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	$ 31,997,000		$ 33,819,000
Amortization of Intangible Assets	1,871,000	$ 2,206,000
Dividends received from equity method investment	12,232,000	9,993,000
Loans	24,499,022,000		23,414,262,000
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	6,700,000		6,800,000
Amortization of Intangible Assets	128,000	188,000
Accretion income	243,000	452,000
Dividends received from equity method investment	12,200,000	10,000,000
Payments to Acquire Loans Held-for-investment	0	$ 74,600,000
Loans	$ 297,600,000		$ 319,100,000