Loans - Additional Information (Details)		12 Months Ended
		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfer of Portfolio Loans and Leases to Held-for-sale		$ 1,790,000,000	$ 3,280,000,000	$ 280,000,000
Transfer of Loans Held-for-sale to Portfolio Loans		741,000,000	44,000,000	$ 43,000,000
Loans held for investment sold		2,071,000,000	3,994,000,000
Gain (Loss) on Sales of Loans, Net		22,000,000	83,000,000
Long-term Debt	[1]	8,462,000,000	13,022,000,000
Other Short-term Borrowings		1,024,000,000	5,634,000,000
Letters of Credit Outstanding, Amount		6,700,000,000	7,900,000,000
Other Real Estate	[2]	56,000,000	99,000,000
Loans and Leases Receivable, Impaired, Commitment to Lend		4,000,000	1,000,000
Loans held for investment	[3]	$ 136,442,000,000	$ 133,112,000,000
Government Guarantee Percent		2.00%
Current Weighted Average FICO Score on Mortgages With Potential Concentration of Credit Risk		745	738
Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 2,600,000,000	$ 2,500,000,000
Accruing TDRs current		97.00%	96.00%
Mortgage Loans in Process of Foreclosure, Amount	[4]	$ 152,000,000	$ 194,000,000
Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans in Process of Foreclosure, Amount	[4]	112,000,000	152,000,000
Proceeds due from FHA or VA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans in Process of Foreclosure, Amount	[4]	141,000,000	179,000,000
Other Real Estate	[4]	$ 52,000,000	$ 57,000,000
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current		31.00%	28.00%
Loans held for investment		$ 629,000,000	$ 632,000,000
Government Guarantee Percent			0.00%
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current		78.00%	79.00%
Loans held for investment		$ 4,922,000,000	$ 4,827,000,000
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Real Estate	[2]	11,000,000	16,000,000
Loans held for investment		75,252,000,000	73,392,000,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Real Estate	[2]	39,000,000	75,000,000
Loans held for investment		38,928,000,000	38,775,000,000
Mortgage Loans on Real Estate		0.29	0.29
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	13,171,000,000	14,264,000,000
Minimum [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans And Leases Receivable Individually Evaluated For Impairment		3,000,000
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Foreign		1,600,000,000	1,300,000,000
Home Equity Line of Credit [Member] | Credit Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unused Commitments to Extend Credit		10,500,000,000	10,900,000,000
Mortgage Loans on Real Estate [Member] | Credit Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unused Commitments to Extend Credit		3,200,000,000	3,300,000,000
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Short-term Borrowings		0	4,000,000,000
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term Debt		408,000,000	4,000,000,000
Federal Reserve Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral		23,600,000,000	26,500,000,000
Line of Credit Facility, Remaining Borrowing Capacity		17,200,000,000	18,400,000,000
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral		33,700,000,000	31,200,000,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 28,500,000,000	$ 24,300,000,000

[1] Includes debt of consolidated VIEs of $259 million and $302 million at December 31, 2015 and December 31, 2014, respectively.

[2] Does not include foreclosed real estate related to loans insured by the FHA or the VA. Proceeds due from the FHA and the VA are recorded as a receivable in other assets in the Consolidated Balance Sheets until the property is conveyed and the funds are received. The receivable related to proceeds due from the FHA or the VA totaled $52 million and $57 million at December 31, 2015 and 2014, respectively.

[3] Includes loans of consolidated VIEs of $246 million and $288 million at December 31, 2015 and December 31, 2014, respectively.

[4] Nonaccruing restructured loans are included in total nonaccrual/NPLs.

[5] Excludes $629 million and $632 million of guaranteed residential loans at December 31, 2015 and 2014, respectively.