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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.

No definition available.

Name:	us-gaap_DerivativeLineItems
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Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

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Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DerivativeRemainingMaturity1
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The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=121549185&loc=d3e80748-113994

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Maximum amount of time remaining before foreign currency exchange rate derivatives mature or expire, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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Derivative contract maturity period, maximum, per the Company's policy.

No definition available.

Name:	wu_DerivativePolicyContractMaturityPeriodMaximum
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Derivative Policy Targeted Weighted Average Maturity

No definition available.

Name:	wu_DerivativePolicyTargetedWeightedAverageMaturity
Namespace Prefix:	wu_
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Balance Type:	na
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Represents revenue based on the difference between the exchange rate set by the Company to the customer and the rate at which the Company or its agents are able to acquire currency.

No definition available.

Name:	wu_ForeignExchangeRevenues
Namespace Prefix:	wu_
Data Type:	xbrli:monetaryItemType
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Name:	us-gaap_StatementBusinessSegmentsAxis=wu_BusinessSolutionsMember
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Name:	srt_RangeAxis=srt_MinimumMember
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