Deposits and Borrowings - Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations	$ 59,468	$ 58,134
Debt and Capital Lease Obligations	$ 60,460	59,115
Securitized debt obligations
Debt Instrument [Line Items]
Weighted average interest rate	1.61%
Long-term debt	$ 18,826	16,166
Total senior and subordinated notes
Debt Instrument [Line Items]
Long-term debt	$ 23,431	21,837
Senior notes \| Total unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.58%
Long-term debt	$ 18,899	17,757
Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.65%
Long-term debt	$ 17,546	16,559
Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	1.73%
Long-term debt	$ 1,353	1,198
Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Weighted average interest rate	4.09%
Long-term debt	$ 4,532	4,080
FHLB advances
Debt Instrument [Line Items]
Weighted average interest rate	0.64%
Long-term debt	$ 17,179	20,098
Capital Lease Obligations
Debt Instrument [Line Items]
Weighted average interest rate	4.17%
Long-term debt	$ 32	33
FHLB Advance and Capital Lease Obligation
Debt Instrument [Line Items]
Long-term debt	$ 17,211	$ 20,131
Minimum [Member] \| Securitized debt obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.74%
Minimum [Member] \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Minimum [Member] \| Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.56%
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	0.45%
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	2.06%
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	6.41%
Maximum [Member] \| Capital Lease Obligations
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	12.86%

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
-Section S99
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-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
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