Capital One Financial Corporation (Parent Company Only) - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net income	$ 4,887	$ 7,360	$ 12,390
Adjustments to reconcile net income (loss) to net cash from operating activities:
Net cash from operating activities	20,575	13,809	12,310
Investing activities:
Net cash used in investing activities	(21,920)	(29,738)	(31,501)
Common stock:
Net proceeds from issuances	299	276	253
Dividends paid	(931)	(950)	(1,148)
Preferred stock:
Net proceeds from issuances	0	0	2,052
Dividends paid	(228)	(228)	(274)
Redemptions	0	0	(2,100)
Purchases of treasury stock	(718)	(4,948)	(7,605)
Proceeds from share-based payment activities	10	19	55
Net cash from financing activities	13,844	25,131	474
Changes in cash, cash equivalents and restricted cash for securitization investors	12,499	9,202	(18,717)
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	31,256	22,054	40,771
Cash, cash equivalents and restricted cash for securitization investors, end of the period	43,755	31,256	22,054
Parent Company
Operating activities:
Net income	4,887	7,360	12,390
Adjustments to reconcile net income (loss) to net cash from operating activities:
Equity in undistributed earnings of subsidiaries	(1,936)	(3,250)	1,360
Other operating activities	623	(2,429)	(4,523)
Net cash from operating activities	3,574	1,681	9,227
Investing activities:
Changes in investments in subsidiaries	0	0	3,521
Proceeds from paydowns and maturities of securities available for sale	103	96	141
Purchases of securities available for sale	(69)	(10)	0
Changes in loans to subsidiaries	371	1,139	(1,925)
Net cash used in investing activities	405	1,225	1,737
Financing activities:
Issuance of senior and subordinated notes	8,219	9,271	4,487
Maturities and paydowns of senior and subordinated notes	(6,989)	(1,250)	(2,750)
Common stock:
Net proceeds from issuances	299	276	253
Dividends paid	(931)	(950)	(1,148)
Preferred stock:
Net proceeds from issuances	0	0	2,052
Dividends paid	(228)	(228)	(274)
Redemptions	0	0	(2,100)
Purchases of treasury stock	(718)	(4,948)	(7,605)
Proceeds from share-based payment activities	10	19	55
Net cash from financing activities	(338)	2,190	(7,030)
Changes in cash, cash equivalents and restricted cash for securitization investors	3,641	5,096	3,934
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	22,006	16,910	12,976
Cash, cash equivalents and restricted cash for securitization investors, end of the period	$ 25,647	$ 22,006	$ 16,910