Deposits and Borrowings - Long-Term Debt (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations	$ 58,134	$ 31,377
Debt and Capital Lease Obligations	$ 59,115	48,457
Securitized debt obligations
Debt Instrument [Line Items]
Interest rate, minimum	0.37%
Interest rate, maximum	5.75%
Weighted average interest rate	1.46%
Long-term debt	$ 16,166	11,624
Total senior and subordinated notes
Debt Instrument [Line Items]
Long-term debt	$ 21,837	18,684
Senior notes \| Total unsecured senior debt
Debt Instrument [Line Items]
Weighted average interest rate	2.61%
Long-term debt	$ 17,757	16,054
Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Interest rate, minimum	1.15%
Interest rate, maximum	6.75%
Weighted average interest rate	2.72%
Long-term debt	$ 16,559	15,174
Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Interest rate, minimum	0.86%
Interest rate, maximum	1.51%
Weighted average interest rate	1.11%
Long-term debt	$ 1,198	880
Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Interest rate, minimum	3.38%
Interest rate, maximum	8.80%
Weighted average interest rate	4.70%
Long-term debt	$ 4,080	2,630
FHLB advances
Debt Instrument [Line Items]
Interest rate, minimum	0.28%
Interest rate, maximum	6.41%
Weighted average interest rate	0.40%
Long-term debt	$ 20,098	1,069
Capital Lease Obligations
Debt Instrument [Line Items]
Interest rate, minimum	3.09%
Interest rate, maximum	12.86%
Weighted average interest rate	4.17%
Long-term debt	$ 33	0
FHLB Advance and Capital Lease Obligation
Debt Instrument [Line Items]
Long-term debt	$ 20,131	$ 1,069

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+ References

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 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 20, 22
-Article 5

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section H

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