Loans and Allowance for Loan Losses - LTV Ratios (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 32,088	$ 29,801
Percentage of total	100.00%	100.00%
Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 30,707	$ 28,439
Percentage of total	96.00%	95.00%
Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 1,236	$ 1,053
Percentage of total	4.00%	4.00%
Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 57	$ 144
Percentage of total	0.00%	0.00%
Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 88	$ 165
Percentage of total	0.00%	1.00%
Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 31,984	$ 29,654
Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	30,615	28,333
Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	1,228	1,021
Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	54	135
Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	87	165
Consumer | Residential mortgage
Credit quality of consumer loans
Loans categorized by LTV ratio	29,559	27,109
Consumer | Residential mortgage | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	28,479	26,143
Consumer | Residential mortgage | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	1,023	804
Consumer | Residential mortgage | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	13	52
Consumer | Residential mortgage | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	44	110
Consumer | Home Equity loans
Credit quality of consumer loans
Loans categorized by LTV ratio	2,425	2,545
Consumer | Home Equity loans | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	2,136	2,190
Consumer | Home Equity loans | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	205	217
Consumer | Home Equity loans | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	41	83
Consumer | Home Equity loans | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	43	55
Purchased Credit- Impaired | Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	104	147
Purchased Credit- Impaired | Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	92	106
Purchased Credit- Impaired | Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	8	32
Purchased Credit- Impaired | Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	3	9
Purchased Credit- Impaired | Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 1	$ 0