Capital One Financial Corporation (Parent Company Only) - Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, Captions [Line Items]
Interest income	$ 41,938	$ 31,237	$ 25,769
Interest expense	12,697	4,123	1,598
Provision (benefit) for credit losses	10,426	5,847	(1,944)
Non-interest income (loss)	7,546	7,136	6,264
Non-interest expense	20,316	19,163	16,570
Income tax benefit	1,158	1,880	3,415
Net income	4,887	7,360	12,390
Comprehensive income (loss)	6,535	(2,930)	9,270
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest income	1,715	595	151
Interest expense	2,160	969	392
Provision (benefit) for credit losses	(1)	(1)	(1)
Dividends from subsidiaries	3,300	4,352	13,970
Non-interest income (loss)	91	(15)	(26)
Non-interest expense	70	35	36
Income before income taxes and equity in undistributed earnings of subsidiaries	2,877	3,929	13,668
Income tax benefit	(73)	(181)	(82)
Equity in undistributed earnings of subsidiaries	1,937	3,250	(1,360)
Net income	4,887	7,360	12,390
Other comprehensive income (loss), net of tax	$ 1,648	(10,290)	(3,120)
Comprehensive income (loss)		$ (2,930)	$ 9,270