Equity method investment - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	$ 40,130,000		$ 42,336,000
Amortization of Intangible Assets	2,206,000	$ 2,520,000
Dividends received from equity method investment	9,993,000	7,957,000
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	7,400,000		$ 7,600,000
Amortization of Intangible Assets	188,000	293,000
Accretion income	452,000	564,000
Dividends received from equity method investment	10,000,000.0	8,000,000.0
Payments to Acquire Loans Held-for-investment	$ 74,600,000	$ 0