Capital One Financial Corporation (Parent Company Only) - Statements of Income (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
Condensed Income Statements, Captions [Line Items]
Interest from temporary investments	$ 6,009	$ 5,794	$ 5,571	$ 5,517	$ 5,384	$ 5,164	$ 4,937	$ 4,974	$ 22,891	$ 20,459	$ 19,397
Interest expense	562	517	478	461	423	404	400	398	2,018	1,625	1,579
Non-interest income	1,119	1,184	1,161	1,164	1,233	1,140	1,135	1,071	4,628	4,579	4,472
Non-interest expense	3,679	3,361	3,295	3,223	3,480	3,160	3,307	3,049	13,558	12,996	12,180
Income tax (benefit)	342	496	424	452	426	530	384	529	1,714	1,869	2,146
Net income	$ 791	$ 1,005	$ 942	$ 1,013	$ 920	$ 1,114	$ 863	$ 1,153	3,751	4,050	4,428
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									3,418	3,864	4,870
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest from temporary investments									120	120	114
Interest expense									258	185	204
Dividends from Subsidiaries									3,936	450	3,449
Non-interest income									(13)	10	53
Non-interest expense									48	178	85
Income before income taxes and equity in undistributed earnings of subsidiaries									3,737	217	3,327
Income tax (benefit)									(79)	(67)	11
Income (loss) from subsidiary including discontinued operations, net of tax									(65)	3,766	1,112
Net income									3,751	4,050	4,428
Other Comprehensive Income (Loss), Net of Tax									(333)	(186)	442
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									$ 3,418	$ 3,864	$ 4,870