Capital One Financial Corporation (Parent Company Only) - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities:
Net income	$ 7,360	$ 12,390	$ 2,714
Adjustments to reconcile net income (loss) to net cash from operating activities:
Net cash from operating activities	13,809	12,310	16,699
Investing activities:
Net cash from investing activities	(29,738)	(31,501)	(14,841)
Common stock:
Net proceeds from issuances	276	253	241
Dividends paid	(950)	(1,148)	(460)
Preferred stock:
Net proceeds from issuances	0	2,052	1,330
Dividends paid	(228)	(274)	(280)
Redemptions	0	(2,100)	(1,375)
Purchases of treasury stock	(4,948)	(7,605)	(393)
Proceeds from share-based payment activities	19	55	62
Net cash from (used in) financing activities	25,131	474	25,164
Changes in cash and cash equivalents	9,202	(18,717)	27,022
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	22,054	40,771	13,749
Cash, cash equivalents and restricted cash for securitization investors, end of the period	31,256	22,054	40,771
Parent Company
Operating activities:
Net income	7,360	12,390	2,714
Adjustments to reconcile net income (loss) to net cash from operating activities:
Equity in undistributed earnings of subsidiaries	(3,250)	1,360	(102)
Other operating activities	(2,429)	(4,523)	1,217
Net cash from operating activities	1,681	9,227	3,829
Investing activities:
Changes in investments in subsidiaries	0	3,521	(217)
Proceeds from paydowns and maturities of securities available for sale	96	141	117
Debt Securities, Available-for-Sale, Purchased with Credit Deterioration, Amount at Purchase Price	(10)	0	0
Changes in loans to subsidiaries	1,139	(1,925)	(2,019)
Net cash from investing activities	1,225	1,737	(2,119)
Financing activities:
Issuance of senior and subordinated notes	9,271	4,487	1,991
Maturities and paydowns of senior and subordinated notes	(1,250)	(2,750)	(2,900)
Common stock:
Net proceeds from issuances	276	253	241
Dividends paid	(950)	(1,148)	(460)
Preferred stock:
Net proceeds from issuances	0	2,052	1,330
Dividends paid	(228)	(274)	(280)
Redemptions	0	(2,100)	(1,375)
Purchases of treasury stock	(4,948)	(7,605)	(393)
Proceeds from share-based payment activities	19	55	62
Net cash from (used in) financing activities	2,190	(7,030)	(1,784)
Changes in cash and cash equivalents	5,096	3,934	(74)
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	16,910	12,976	13,050
Cash, cash equivalents and restricted cash for securitization investors, end of the period	$ 22,006	$ 16,910	$ 12,976