Types and Classifications of Derivative Instruments Designated as Hedges (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Fair Value Asset	$ 3,047.6	$ 1,864.5
Fair Value Liability	2,767.6	2,261.8
Asset And Liability Management
Derivative [Line Items]
Notional Value	9,942.9	7,556.0
Fair Value Asset	494.8	198.8
Fair Value Liability	42.2	38.0
Asset And Liability Management \| Fair Value Hedges \| Senior Notes and Long- Term Subordinated Debt \| Interest Rate Swaps
Derivative [Line Items]
Notional Value	1,250.0	1,250.0
Fair Value Asset	71.8	104.6
Fair Value Liability	3.3	2.2
Asset And Liability Management \| Fair Value Hedges \| Securities Available for Sale \| Interest Rate Swaps
Derivative [Line Items]
Notional Value	3,873.4	3,042.1
Fair Value Asset	88.3	10.8
Fair Value Liability	16.8	19.8
Asset And Liability Management \| Cash Flow Hedges \| Forecasted Foreign Currency Denominated Transactions \| Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	329.3	367.4
Fair Value Asset	8.5	8.5
Fair Value Liability	7.8	13.8
Asset And Liability Management \| Cash Flow Hedges \| Foreign Currency Denominated Investment Securities \| Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	1,431.6	0.0
Fair Value Asset	151.5	0.0
Fair Value Liability	0.8	0.0
Asset And Liability Management \| Cash Flow Hedges \| Securities Available for Sale \| Interest Rate Option Contracts
Derivative [Line Items]
Notional Value	975.0	935.0
Fair Value Asset	0.1	2.0
Fair Value Liability	2.7	0.7
Asset And Liability Management \| Net Investment Hedges \| Net Investments in Non-U.S. Affiliates \| Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	2,083.6	1,961.5
Fair Value Asset	174.6	72.9
Fair Value Liability	$ 10.8	$ 1.5

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

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No definition available.

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