Loans and Allowance for Loan Losses (Details 9) - Consumer portfolio - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2017	Dec. 31, 2016
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 34,608	$ 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		$ 33,695	$ 30,707
Percentage of total loans categorized by LTV ratio		98.00%	96.00%
LTV Ratio Greater than 80 Percent and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 803	$ 1,236
Percentage of total loans categorized by LTV ratio		2.00%	4.00%
LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		$ 40	$ 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]	$ 70	$ 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		$ 32,206	$ 29,639
Residential mortgage | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		31,586	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		577	1,030
Residential mortgage | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		8	16
Residential mortgage | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	35	46
Home Equity loans
Credit quality of consumer loans
Loans categorized by LTV ratio		2,402	2,450
Home Equity loans | LTV Ratio Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		2,109	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		226	206
Home Equity loans | LTV Ratio Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio		32	41
Home Equity loans | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	[1]	$ 35	$ 43

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