Equity method investment - Financial Position and Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Assets	$ 39,400,378		$ 38,469,399
Liabilities	34,119,428		33,158,792
Total liabilities and shareholders' equity	39,400,378		38,469,399
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Assets	3,106,382		2,724,542
Liabilities	2,706,875		2,355,256
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	399,507		369,286
Total liabilities and shareholders' equity	3,106,382		$ 2,724,542
Revenues	238,612	$ 157,623
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 69,826	$ 58,562