Loans and Allowance for Loan Losses (Details 9) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 29,904	$ 29,801
Percentage of total loans categorized by LTV ratio		100.00%	100.00%
Consumer | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 28,614	$ 28,439
Percentage of total loans categorized by LTV ratio		96.00%	95.00%
Consumer | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 1,001	$ 1,053
Percentage of total loans categorized by LTV ratio		3.00%	4.00%
Consumer | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 136	$ 144
Percentage of total loans categorized by LTV ratio		0.00%	0.00%
Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 153	$ 165	[1]
Percentage of total loans categorized by LTV ratio		1.00%	1.00%
Consumer portfolio
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 29,766	$ 29,654
Consumer portfolio | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		28,513	28,333
Consumer portfolio | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		974	1,021
Consumer portfolio | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		127	135
Consumer portfolio | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	152	165
Consumer portfolio | Residential mortgage
Credit quality of consumer loans
Loans categorized by LTV ratio			27,109
Consumer portfolio | Residential mortgage | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		26,396	26,143
Consumer portfolio | Residential mortgage | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		764	804
Consumer portfolio | Residential mortgage | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		48	52
Consumer portfolio | Residential mortgage | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	52	110
Consumer portfolio | Home Equity loans
Credit quality of consumer loans
Loans categorized by LTV ratio		2,506	2,545
Consumer portfolio | Home Equity loans | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		2,117	2,190
Consumer portfolio | Home Equity loans | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		210	217
Consumer portfolio | Home Equity loans | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		79	83
Consumer portfolio | Home Equity loans | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	100	55
Purchased credit-impaired loans | Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio		138	147
Purchased credit-impaired loans | Consumer | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		101	106
Purchased credit-impaired loans | Consumer | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		27	32
Purchased credit-impaired loans | Consumer | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		9	9
Purchased credit-impaired loans | Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 1	$ 0

[1] Represents loans for which management was not able to obtain refreshed property values.