Capital One Financial Corporation (Parent Company Only) - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets:
Cash and cash equivalents	$ 8,023	$ 7,242	$ 6,291	$ 11,058
Securities available for sale	39,061	39,508
Other assets	16,450	15,382
Total assets	334,048	308,167
Liabilities:
Senior and subordinated notes	21,837	18,684
Other borrowings	20,131	17,269
Accrued expenses and other liabilities	9,629	8,855
Total liabilities	286,764	263,114
Stockholders’ equity:
Total stockholders’ equity	47,284	45,053	41,632	40,425
Total liabilities and stockholders’ equity	334,048	308,167
Parent Company
Assets:
Cash and cash equivalents	7,245	8,262	$ 7,185	$ 7,342
Investment in subsidiaries	48,676	44,993
Loans to subsidiaries	521	1,494
Securities available for sale	905	961
Other assets	739	618
Total assets	58,086	56,328
Liabilities:
Senior and subordinated notes	8,657	8,907
Other borrowings	1,591	1,573
Accrued expenses and other liabilities	554	795
Total liabilities	10,802	11,275
Stockholders’ equity:
Total stockholders’ equity	47,284	45,053
Total liabilities and stockholders’ equity	$ 58,086	$ 56,328