Capital One Financial Corporation (Parent Company Only) - Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Income Statements, Captions [Line Items]
Interest income	$ 25,769	$ 26,033	$ 28,513
Interest expense	1,598	3,120	5,173
Provision (benefit) for credit losses	(1,944)	10,264	6,236
Non-interest income (loss)	6,264	5,610	5,253
Non-interest expense	16,570	15,056	15,483
Income tax benefit	3,415	486	1,341
Net income (loss)	12,390	2,714	5,546
Comprehensive income	9,270	5,060	7,077
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest income	151	186	442
Interest expense	392	510	798
Provision (benefit) for credit losses	(1)	0	0
Dividends from subsidiaries	13,970	3,003	3,276
Non-interest income (loss)	(26)	(127)	(21)
Non-interest expense	36	33	60
Income before income taxes and equity in undistributed earnings of subsidiaries	13,668	2,519	2,839
Income tax benefit	(82)	(93)	(138)
Equity in undistributed earnings of subsidiaries	(1,360)	102	2,569
Net income (loss)	12,390	2,714	5,546
Other comprehensive income (loss), net of tax	(3,120)	2,346	1,531
Comprehensive income	$ 9,270	$ 5,060	$ 7,077