Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015 item	Dec. 31, 2014 item
Derivative
Number of Hedging instruments	0	0
Derivatives not designated as hedging instruments
Derivative
Notional Amount	4,537.2	4,344.7
Derivative Assets	77.1	53.2
Derivative Liabilities	77.4	52.9
Derivatives not designated as hedging instruments \| Option contracts
Derivative
Notional Amount	1.8	1.9
Derivative Assets	0.3	0.4
Derivatives not designated as hedging instruments \| Interest-Rate Contracts
Derivative
Notional Amount	3,660.0	3,531.8
Derivative Assets	60.2	45.5
Derivative Liabilities	61.4	46.0
Derivatives not designated as hedging instruments \| Interest-Rate Swaps
Derivative
Notional Amount	3,221.1	3,094.5
Derivative Assets	59.8	44.7
Derivative Liabilities	61.0	45.2
Derivatives not designated as hedging instruments \| Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	438.9	437.3
Derivative Assets	0.4	0.8
Derivative Liabilities	0.4	0.8
Derivatives not designated as hedging instruments \| Spot and forward contracts
Derivative
Notional Amount	866.2	802.7
Derivative Assets	15.1	6.1
Derivative Liabilities	16.0	6.6
Derivatives not designated as hedging instruments \| Foreign Exchange Contracts
Derivative
Notional Amount	872.2	808.7
Derivative Assets	15.4	6.4
Derivative Liabilities	16.0	6.9
Derivatives not designated as hedging instruments \| Foreign Exchange Contracts \| Options purchased \| Purchase
Derivative
Notional Amount	3.0	3.0
Derivative Assets	0.1	0.1
Derivative Liabilities	0.1	0.1
Derivatives not designated as hedging instruments \| Foreign Exchange Contracts \| Options purchased \| Sale
Derivative
Notional Amount	3.0	3.0
Derivative Assets	0.2	0.2
Derivative Liabilities	0.2	0.2
Equity Warrants \| Derivatives not designated as hedging instruments
Derivative
Notional Amount	3.2	2.3
Derivative Assets	1.2	0.9

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 not subject to a master netting arrangement and elected not to be offset.

+ 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=34720828&loc=SL20225862-175312

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- Definition

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 not subject to a master netting arrangement and elected not to be offset.

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- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5579245-113959

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