Other income and operating expenses - Income and Expenses Related to Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other income
Interest income	$ 945,814	$ 663,217	$ 395,196
Interest and Fee Income	930,572	634,426	374,688
Other operating expenses
Direct operating expenses	7,345	12,906	24,337
R&D reserve	3,229	6,977	(10,224)
Interest expense	716,468	392,360	204,368
Total other operating expenses	59,591	47,653	49,903
Net income	348,411	203,163	$ 159,974
Paycheck Protection Program loans
Other income
Interest and Fee Income	13,462	67,417
Other operating expenses
Total other operating expenses	646	1,910
Net income	12,816	65,507
Paycheck Protection Program loans | Other Income
Other income
Repair and denial reserve	3,055	7,530
Paycheck Protection Program loans | Servicing income
Other income
LSP fee income	57	5,369
Paycheck Protection Program loans | Interest income
Other income
Interest income	10,350	54,518
Paycheck Protection Program loans | Other operating expenses
Other operating expenses
Direct operating expenses	233	211
Paycheck Protection Program loans | Interest expense
Other operating expenses
Interest expense	$ 413	$ 1,699