Equity method investment - Financial Position and Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Assets	$ 40,121,292		$ 40,121,292		$ 38,469,399
Liabilities	34,806,053		34,806,053		33,158,792
Total liabilities and shareholders' equity	40,121,292		40,121,292		38,469,399
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Assets	3,465,380		3,465,380		2,724,542
Liabilities	2,980,649		2,980,649		2,355,256
Equity interests	484,731		484,731		369,286
Total liabilities and shareholders' equity	3,465,380		3,465,380		$ 2,724,542
Revenues	297,947	$ 178,984	536,559	$ 336,607
Net income	$ 107,207	$ 62,353	$ 177,033	$ 120,915