Capital One Financial Corporation (Parent Company Only) - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income (loss)	$ 12,390	$ 2,714	$ 5,546
Adjustments to reconcile net income (loss) to net cash from operating activities:
Net cash from operating activities	12,310	16,699	16,639
Investing activities:
Net cash from investing activities	(31,501)	(14,841)	(22,998)
Common stock:
Net proceeds from issuances	253	241	199
Dividends paid	(1,148)	(460)	(753)
Preferred stock:
Net proceeds from issuances	2,052	1,330	1,462
Dividends paid	(274)	(280)	(282)
Redemptions	(2,100)	(1,375)	(1,000)
Purchases of treasury stock	(7,605)	(393)	(1,481)
Proceeds from share-based payment activities	55	62	17
Net cash from financing activities	474	25,164	6,619
Changes in cash and cash equivalents	(18,717)	27,022	260
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	40,771	13,749	13,489
Cash, cash equivalents and restricted cash for securitization investors, end of the period	22,054	40,771	13,749
Parent Company
Operating activities:
Net income (loss)	12,390	2,714	5,546
Adjustments to reconcile net income (loss) to net cash from operating activities:
Equity in undistributed earnings of subsidiaries	1,360	(102)	(2,569)
Other operating activities	(4,523)	1,217	216
Net cash from operating activities	9,227	3,829	3,193
Investing activities:
Changes in investments in subsidiaries	3,521	(217)	704
Proceeds from paydowns and maturities of securities available for sale	141	117	111
Changes in loans to subsidiaries	(1,925)	(2,019)	(1,302)
Net cash from investing activities	1,737	(2,119)	(487)
Financing activities:
Issuance of senior and subordinated notes	4,487	1,991	2,646
Maturities and paydowns of senior and subordinated notes	(2,750)	(2,900)	(750)
Common stock:
Net proceeds from issuances	253	241	199
Dividends paid	(1,148)	(460)	(753)
Preferred stock:
Net proceeds from issuances	2,052	1,330	1,462
Dividends paid	(274)	(280)	(282)
Redemptions	(2,100)	(1,375)	(1,000)
Purchases of treasury stock	(7,605)	(393)	(1,481)
Proceeds from share-based payment activities	55	62	17
Net cash from financing activities	(7,030)	(1,784)	58
Changes in cash and cash equivalents	3,934	(74)	2,764
Cash, cash equivalents and restricted cash for securitization investors, beginning of the period	12,976	13,050	10,286
Cash, cash equivalents and restricted cash for securitization investors, end of the period	16,910	12,976	13,050
Supplemental information:
Decrease in investment in subsidiaries	0	0	1,508
Decrease in borrowings from subsidiaries	$ 0	$ 0	$ 1,671