Equity method investment - Financial Position and Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Assets	$ 45,119,587		$ 41,970,021
Liabilities	39,435,459		36,450,629
Total liabilities and shareholders' equity	45,119,587		41,970,021
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Assets	4,470,032		4,375,643
Liabilities	3,916,653		3,821,725
Equity interests	553,379		553,918
Total liabilities and shareholders' equity	4,470,032		$ 4,375,643
Revenues	301,951	$ 238,612
Net income	$ 46,643	$ 69,826