Deposits and Borrowings - Long-Term Debt (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Securitized debt obligations	$ 18,358	$ 18,826
Long-term Debt and Capital Lease Obligations	48,996	59,468
Debt and Capital Lease Obligations	$ 49,954	60,460
Securitized debt obligations
Debt Instrument [Line Items]
Weighted average interest rate	1.88%
Long-term debt		18,826
Total senior and subordinated notes
Debt Instrument [Line Items]
Long-term debt	$ 28,478	23,431
Senior notes \| Total unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.68%
Long-term debt	$ 23,922	18,899
Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.76%
Long-term debt	$ 21,174	17,546
Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.08%
Long-term debt	$ 2,748	1,353
Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Weighted average interest rate	4.09%
Long-term debt	$ 4,556	4,532
FHLB advances
Debt Instrument [Line Items]
Weighted average interest rate	1.24%
Long-term debt	$ 2,114	17,179
Capital Lease Obligations
Debt Instrument [Line Items]
Weighted average interest rate	5.90%
Long-term debt	$ 46	32
FHLB Advance and Capital Lease Obligation
Debt Instrument [Line Items]
Long-term debt	$ 2,160	$ 17,211
Minimum [Member] \| Securitized debt obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Minimum [Member] \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.50%
Minimum [Member] \| Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.85%
Minimum [Member] \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.38%
Minimum [Member] \| FHLB advances
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Minimum [Member] \| Capital Lease Obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.09%
Maximum [Member] \| Securitized debt obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Maximum [Member] \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.75%
Maximum [Member] \| Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.33%
Maximum [Member] \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.80%
Maximum [Member] \| FHLB advances
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.54%
Maximum [Member] \| Capital Lease Obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	12.86%

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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