Fair Value Measurements (Level 3 Significant Unobservable Inputs) (Details) - Fair Value, Measurements, Recurring - Level 3 - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Swaps Related to Sale of Certain Visa Class B Common Shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value swaps	$ 27.7	$ 0.0
Swaps Related to Sale of Certain Visa Class B Common Shares \| Group One
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation technique	Discounted Cash Flow	Discounted Cash Flow
Unobservable inputs	Visa Class A Appreciation	Visa Class A Appreciation
Swaps Related to Sale of Certain Visa Class B Common Shares \| Group Two
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable inputs	Conversion Rate	Conversion Rate
Swaps Related to Sale of Certain Visa Class B Common Shares \| Group Three
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable inputs	Expected Duration	Expected Duration
Swaps Related to Sale of Certain Visa Class B Common Shares \| Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instrument visa class A appreciation	7.00%	7.00%
Financial instrument conversion rate	1.63%	1.63%
Financial instrument expected conversion rate	1 year 6 months	1 year 6 months
Swaps Related to Sale of Certain Visa Class B Common Shares \| Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instrument visa class A appreciation	11.00%	11.00%
Financial instrument conversion rate	1.65%	1.65%
Financial instrument expected conversion rate	4 years	4 years 6 months
Auction Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value auction rate securities	$ 4.1	$ 0.0
Auction Rate \| Group One
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation technique	Comparables	Comparables
Unobservable inputs	Price	Price
Auction Rate \| Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments fair value assumptions price per share	$ 87	$ 84
Auction Rate \| Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments fair value assumptions price per share	$ 99	$ 99

Fair Value Assets And Liabilities Measured On Recurring Basis Significant Unobservable Inputs

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Financial Instruments Fair Value Assumptions Conversion Rate

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Description of the inputs and valuation technique(s) used to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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