Capital One Financial Corporation (Parent Company Only) - Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 791	$ 1,005	$ 942	$ 1,013	$ 920	$ 1,114	$ 863	$ 1,153	$ 3,751	$ 4,050	$ 4,428
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net cash from operating activities									11,856	10,127	9,304
Investing activities:
Purchase of securities available for sale									(14,154)	(12,200)	(12,650)
Net cash from investing activities									(25,630)	(29,726)	(15,991)
Common Stock
Net proceeds from issuances									131	111	100
Dividends paid									(812)	(816)	(679)
Preferred Stock
Net proceeds from issuances									1,066	1,472	969
Dividends paid									(214)	(158)	(67)
Purchases of treasury stock									(3,661)	(2,441)	(2,045)
Proceeds from share-based payment activities									142	85	146
Net cash from financing activities									15,727	20,380	7,638
Changes in cash and cash equivalents									1,953	781	951
Cash and cash equivalents at beginning of the period				8,023				7,242	8,023	7,242	6,291
Cash and cash equivalents at end of the period	9,976				8,023				9,976	8,023	7,242
Parent Company
Operating activities:
Net income									3,751	4,050	4,428
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries									65	(3,766)	(1,112)
Other operating activities									(10)	(300)	(83)
Net cash from operating activities									3,806	(16)	3,233
Investing activities:
Net payments (to) from subsidiaries									(163)	(172)	94
Proceeds from paydowns and maturities of securities available for sale									71	65	50
Purchase of securities available for sale									0	0	(143)
Changes in loans to subsidiaries									(71)	973	(7)
Net cash from investing activities									(163)	866	(6)
Financing activities:
Changes in borrowings from subsidiaries									19	18	28
Proceeds from issuance of senior notes and sub notes									1,487	2,487	1,498
Proceeds from paydowns and maturities of senior and subordinated notes									(1,750)	(2,625)	(2,100)
Common Stock
Net proceeds from issuances									131	111	100
Dividends paid									(812)	(816)	(679)
Preferred Stock
Net proceeds from issuances									1,066	1,472	969
Dividends paid									(214)	(158)	(67)
Purchases of treasury stock									(3,661)	(2,441)	(2,045)
Proceeds from share-based payment activities									142	85	146
Net cash from financing activities									(3,592)	(1,867)	(2,150)
Changes in cash and cash equivalents									51	(1,017)	1,077
Cash and cash equivalents at beginning of the period				$ 7,245				$ 8,262	7,245	8,262	7,185
Cash and cash equivalents at end of the period	$ 7,296				$ 7,245				$ 7,296	$ 7,245	$ 8,262