Loans and Allowance for Loan Losses (Details 9) - Consumer portfolio - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 33,260	$ 32,089
Percentage of total loans categorized by LTV ratio		100.00%	100.00%
LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 31,824	$ 30,707
Percentage of total loans categorized by LTV ratio		96.00%	96.00%
LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 1,309	$ 1,236
Percentage of total loans categorized by LTV ratio		4.00%	4.00%
LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 51	$ 57
Percentage of total loans categorized by LTV ratio		0.00%	0.00%
No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	$ 76	$ 89
Percentage of total loans categorized by LTV ratio	[1]	0.00%	0.00%
Residential mortgage
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 30,862	$ 29,639
Residential mortgage | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		29,721	28,547
Residential mortgage | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		1,090	1,030
Residential mortgage | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		14	16
Residential mortgage | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	37	46
Home Equity loans
Credit quality of consumer loans
Loans categorized by LTV ratio		2,398	2,450
Home Equity loans | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		2,103	2,160
Home Equity loans | LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		219	206
Home Equity loans | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		37	41
Home Equity loans | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	$ 39	$ 43

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