Capital One Financial Corporation (Parent Company Only) - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Cash and cash equivalents	$ 9,976	$ 8,023	$ 7,242	$ 6,291
Securities available for sale	40,737	39,061
Other assets	18,420	16,450
Total assets	357,033	334,048
Liabilities:
Senior and subordinated notes	23,431	21,837
Other borrowings	17,211	20,131
Accrued expenses and other liabilities	11,964	9,629
Total liabilities	309,519	286,764
Stockholders’ equity:
Total stockholders’ equity	47,514	47,284	45,053	41,632
Total liabilities and stockholders’ equity	357,033	334,048
Parent Company
Assets:
Cash and cash equivalents	7,296	7,245	$ 8,262	$ 7,185
Investment in subsidiaries	48,297	48,676
Loans to subsidiaries	592	521
Securities available for sale	901	905
Other assets	672	739
Total assets	57,758	58,086
Liabilities:
Senior and subordinated notes	8,304	8,657
Other borrowings	1,610	1,591
Accrued expenses and other liabilities	330	554
Total liabilities	10,244	10,802
Stockholders’ equity:
Total stockholders’ equity	47,514	47,284
Total liabilities and stockholders’ equity	$ 57,758	$ 58,086