Capital One Financial Corporation (Parent Company Only) - Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Income Statements, Captions [Line Items]
Interest from temporary investments	$ 5,384	$ 5,164	$ 4,937	$ 4,974	$ 5,045	$ 4,887	$ 4,712	$ 4,753	$ 20,459	$ 19,397	$ 19,898
Interest expense	423	404	400	398	389	390	397	403	1,625	1,579	1,792
Non-interest income	1,233	1,140	1,135	1,071	1,157	1,142	1,153	1,020	4,579	4,472	4,278
Non-interest expense	3,480	3,160	3,307	3,049	3,284	2,985	2,979	2,932	12,996	12,180	12,353
Income tax (benefit)	426	530	384	529	450	536	581	579	1,869	2,146	2,224
Net income	$ 920	$ 1,114	$ 863	$ 1,153	$ 999	$ 1,081	$ 1,194	$ 1,154	4,050	4,428	4,121
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									3,864	4,870	2,510
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest from temporary investments									120	114	94
Interest expense									185	204	250
Dividends from Subsidiaries									450	3,449	5,950
Non-interest income									10	53	33
Non-interest expense									178	85	196
Income before income taxes and equity in undistributed earnings of subsidiaries									217	3,327	5,631
Income tax (benefit)									(67)	11	(66)
Income (loss) from subsidiary including discontinued operations, net of tax									3,766	1,112	(1,576)
Net income									4,050	4,428	4,121
Other Comprehensive Income (Loss), Net of Tax									(186)	442	(1,611)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									$ 3,864	$ 4,870	$ 2,510