Loans and Allowance for Loan Losses - LTV Ratios (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 29,801	$ 31,712
Financing Receivable Recorded Investment Excluding Loans Serviced by Third Parties and Covered Loans	$ 30,436	$ 31,958
Percentage of total loans categorized by LTV ratio	100.00%	100.00%
Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 28,439	$ 29,657
Percentage of total loans categorized by LTV ratio	95.00%	94.00%
Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 1,053	$ 1,745
Percentage of total loans categorized by LTV ratio	4.00%	5.00%
Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 144	$ 228
Percentage of total loans categorized by LTV ratio	0.00%	1.00%
Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 165	$ 82
Percentage of total loans categorized by LTV ratio	1.00%	0.00%
Consumer portfolio
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 29,654	$ 31,517
Financing Receivable Recorded Investment Excluding Loans Serviced by Third Parties and Covered Loans	30,288	31,761
Consumer portfolio | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	28,333	29,526
Consumer portfolio | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	1,021	1,700
Consumer portfolio | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	135	210
Consumer portfolio | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	165	81
Consumer portfolio | Residential mortgage
Credit quality of consumer loans
Loans categorized by LTV ratio		28,715
Financing Receivable Recorded Investment Excluding Loans Serviced by Third Parties and Covered Loans	27,109	28,715
Consumer portfolio | Residential mortgage | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	26,143	27,162
Consumer portfolio | Residential mortgage | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	804	1,430
Consumer portfolio | Residential mortgage | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	52	92
Consumer portfolio | Residential mortgage | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	110	31
Consumer portfolio | Home Equity loans
Credit quality of consumer loans
Loans categorized by LTV ratio	2,545	2,802
Consumer portfolio | Home Equity loans | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	2,190	2,364
Consumer portfolio | Home Equity loans | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	217	270
Consumer portfolio | Home Equity loans | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	83	118
Consumer portfolio | Home Equity loans | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	55	50
Purchased credit-impaired loans | Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	147	195
Financing Receivable Recorded Investment Excluding Loans Serviced by Third Parties and Covered Loans	148	197
Purchased credit-impaired loans | Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	106	131
Purchased credit-impaired loans | Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	32	45
Purchased credit-impaired loans | Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	9	18
Purchased credit-impaired loans | Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 0	$ 1