Loans - Additional Information (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfer of Portfolio Loans and Leases to Held-for-sale		$ 360	$ 1,790	$ 3,280
Transfer of Loans Held-for-sale to Portfolio Loans		30	741	$ 44
Loans held for investment sold		1,600	2,100
Gain (Loss) on Sales of Loans, Net		6	22
Long-term Debt	[1]	11,748	8,462
Other Short-term Borrowings		1,015	1,024
Letters of Credit Outstanding, Amount		7,300	6,700
Loans and Leases Receivable, Impaired, Commitment to Lend		29	4
Loans held for investment	[2]	$ 143,298	$ 136,442
Current Weighted Average FICO Score on Mortgages With Potential Concentration of Credit Risk		751	745
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current		29.00%	31.00%
Loans held for investment		$ 537	$ 629
Government Guarantee Percent		1.00%	2.00%
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment purchased		$ 2,172	$ 1,193
Percentage of Loan Portfolio Current		75.00%	78.00%
Loans held for investment		$ 6,167	$ 4,922
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		78,224	75,252
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 38,990	$ 38,928
Percentage of Loans Held for Investment		27.00%	29.00%
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[3]	$ 11,912	$ 13,171
Geographic Distribution, Foreign [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,200	1,600
Minimum [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans And Leases Receivable Individually Evaluated For Impairment		3	3
Home Equity Line of Credit [Member] | Credit Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unused Commitments to Extend Credit		10,300	10,500
Mortgage Loans on Real Estate [Member] | Credit Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unused Commitments to Extend Credit		4,200	3,200
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term Debt		2,800	408
Federal Reserve Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral		22,600	23,600
Line of Credit Facility, Remaining Borrowing Capacity		17,000	17,200
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral		36,900	33,700
Line of Credit Facility, Remaining Borrowing Capacity		$ 31,900	$ 28,500

[1] Includes debt of consolidated VIEs of $222 million and $259 million at December 31, 2016 and December 31, 2015, respectively.

[2] Includes loans of consolidated VIEs of $211 million and $246 million at December 31, 2016 and December 31, 2015, respectively.

[3] Excludes $537 million and $629 million of guaranteed residential loans at December 31, 2016 and 2015, respectively.