Borrowed Funds (FHLB Borrowings, Bank Notes, Senior Debt and Subordinated Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Borrowed Funds	$ 59,088	$ 52,706
Total FHLB, Senior and Sub Debt	54,299	48,530
Parent Company
Debt Instrument [Line Items]
Borrowed Funds	6,848	6,203
Bank
Debt Instrument [Line Items]
Borrowed Funds	47,451	42,327
Senior Notes \| Parent Company
Debt Instrument [Line Items]
Borrowed Funds	5,203	3,960
Senior Notes \| Bank
Debt Instrument [Line Items]
Borrowed Funds	$ 22,859	19,012
Senior Notes \| Maximum \| Parent Company
Debt Instrument [Line Items]
Stated interest rate	6.70%
Senior Notes \| Maximum \| Bank
Debt Instrument [Line Items]
Stated interest rate	3.30%
Senior Notes \| Minimum \| Parent Company
Debt Instrument [Line Items]
Stated interest rate	1.64%
Senior Notes \| Minimum \| Bank
Debt Instrument [Line Items]
Stated interest rate	1.05%
Subordinated Debt \| Parent Company
Debt Instrument [Line Items]
Borrowed Funds	$ 1,440	2,038
Subordinated Debt \| Bank
Debt Instrument [Line Items]
Borrowed Funds	$ 3,555	5,766
Subordinated Debt \| Maximum \| Parent Company
Debt Instrument [Line Items]
Stated interest rate	6.88%
Subordinated Debt \| Maximum \| Bank
Debt Instrument [Line Items]
Stated interest rate	6.88%
Subordinated Debt \| Minimum \| Parent Company
Debt Instrument [Line Items]
Stated interest rate	3.90%
Subordinated Debt \| Minimum \| Bank
Debt Instrument [Line Items]
Stated interest rate	2.70%
Junior Subordinated Debt \| Parent Company
Debt Instrument [Line Items]
Borrowed Funds	$ 205	205
Stated interest rate	2.05%
FHLB \| Bank
Debt Instrument [Line Items]
Borrowed Funds	$ 21,037	$ 17,549
FHLB \| Maximum \| Bank
Debt Instrument [Line Items]
Stated interest rate	6.35%
FHLB \| Minimum \| Bank
Debt Instrument [Line Items]
Stated interest rate	0.00%

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 excluding other borrowings.

No definition available.

+ Details

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- Definition

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.

+ 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 210.9-03.13,16)
-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 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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