Business and Basis of Presentation (Policies)	6 Months Ended
Business and Basis of Presentation (Policies)	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are unaudited and were prepared in accordance with the instructions for Form 10-Q and Article 10 of Regulation S-X. In compliance with those instructions, certain information and footnote disclosures normally included in annual consolidated financial statements prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") have been condensed or omitted. The unaudited condensed consolidated financial statements in this quarterly report are presented on a consolidated basis and include the accounts of the Company and its majority-owned subsidiaries. Results of operations and cash flows for the interim periods are not necessarily indicative of the results that may be expected for the entire year. All significant intercompany transactions and accounts were eliminated as of June 30, 2018 and December 31, 2017 and for all periods presented. Beginning in the first quarter of 2018, the Company no longer presents the "Derivative gains, net" line item in its Condensed Consolidated Statements of Income for all periods presented due to the early adoption of the new accounting pronouncement to improve the financial reporting of hedging relationships, as further described below. Amounts previously reported in prior periods in "Derivative gains, net" are now reported in "Other income, net" in the Condensed Consolidated Statements of Income. Additionally, certain historical amounts reported in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2017 have been adjusted due to the adoption of an accounting standard related to pension costs, as further described below. In the opinion of management, these condensed consolidated financial statements include all the normal recurring adjustments necessary to fairly present the Company's condensed consolidated results of operations, financial position and cash flows as of June 30, 2018 and for all periods presented. These condensed consolidated financial statements should be read in conjunction with the Company's consolidated financial statements within the Company's Annual Report on Form 10-K for the year ended December 31, 2017. Consistent with industry practice, the accompanying Condensed Consolidated Balance Sheets are unclassified due to the short-term nature of the Company's settlement obligations contrasted with the Company's ability to invest cash awaiting settlement in long-term investment securities.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates.
New Accounting Pronouncements	Recently Adopted Accounting Pronouncements On January 1, 2018, the Company adopted a new accounting standard, as amended, regarding revenue from contracts with customers using the modified retrospective approach. This standard provides guidance on recognizing revenue, including a five-step model to determine when revenue recognition is appropriate. The adoption of this standard did not have a material impact on the Company's financial position and results of operations. Refer to Note 2 for the related additional disclosures. On January 1, 2018, the Company adopted an accounting pronouncement regarding classification and measurement of financial instruments. This standard provides guidance on how entities measure certain equity investments and present changes in fair value. This standard requires that entities measure certain equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income. The Company's money market funds have readily determinable fair values, as disclosed in Note 6, and for those equity investments that are not accounted for under the equity method and that do not have readily determinable fair values, the Company has elected to measure these securities at cost less impairment, adjusted for observable price changes for identical or similar investments of the same issuer. The adoption of this standard did not have a material impact on the Company's financial position, results of operations, or related disclosures. On January 1, 2018, the Company adopted an accounting pronouncement regarding certain intra-entity asset transfers that requires that an entity recognize any income tax consequences when the transfer occurs. The adoption of this standard did not have a material impact on the Company's financial position. On January 1, 2018, the Company retrospectively adopted an accounting pronouncement that requires restricted cash, which is recorded in "Other assets" in the Company's Condensed Consolidated Balance Sheets, to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period amounts shown on the statements of cash flows. The adoption of this standard did not have a significant impact on the Company's statements of cash flows. On January 1, 2018, the Company retrospectively adopted an accounting pronouncement that requires the non-service cost components of defined benefit plan pension costs to be presented in the income statement separately from the service cost component, outside a subtotal of income from operations. The Company has no service costs, as the Company's defined benefit pension plan is frozen. Prior to the adoption of this standard, the Company recorded the non-service costs of the defined benefit pension plan in the "Cost of services" line item of the Condensed Consolidated Statements of Income. After the adoption of this standard, the Company records these costs in the "Other income, net" line item, including for the three and six months ended June 30, 2018 and 2017. The adoption of this standard resulted in reductions to "Cost of services" and "Other income, net" of $0.6 million and $1.2 million for the three and six months ended June 30, 2017, respectively, from the amounts previously reported. On January 1, 2018, the Company elected to adopt an accounting pronouncement to improve the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements. The effects of the standard are recognized prospectively in the Company's financial statements. The adoption of this standard did not have a material impact on the Company's financial position or results of operations, but does require the addition of certain disclosures. Refer to Note 11 for additional information and the related disclosures. In the first quarter of 2018, the Company adopted a new accounting pronouncement that provides entities the option to reclassify tax effects included within accumulated other comprehensive income/(loss) as a result of the United States tax reform legislation enacted in December 2017 (the “Tax Act”) to retained earnings. The adoption of this standard resulted in an increase to "Accumulated other comprehensive loss" and a decrease to "Accumulated deficit" in the Condensed Consolidated Balance Sheet of $31.4 million, which represents the tax effects of the lower federal tax rate on unrealized gains/(losses) on investment securities, hedging activities, and adjustments related to the Company's defined benefit pension plan, in addition to the release of deferred taxes accrued on undistributed earnings of one of the Company's subsidiaries that are no longer owed under the Tax Act. The Company will continue to release tax effects remaining in "Accumulated other comprehensive loss" into income as the individual units of account are sold or otherwise extinguished. Refer to Note 10 for additional information. Accounting Pronouncements Not Yet Adopted In February 2016, the Financial Accounting Standards Board issued a new accounting pronouncement regarding the financial reporting of leasing transactions. This new standard requires a lessee to record assets and liabilities on the balance sheet for the rights and obligations arising from leases with terms of more than 12 months. The Company is required to adopt the new standard on January 1, 2019 using a modified retrospective approach. Management is currently evaluating the potential impact that the adoption of this standard will have on the Company's financial position, results of operations, and related disclosures. In June 2016, the Financial Accounting Standards Board issued a new accounting pronouncement regarding credit losses for financial instruments. The new standard requires entities to measure expected credit losses for certain financial assets held at the reporting date using a current expected credit loss model, which is based on historical experience, adjusted for current conditions and reasonable and supportable forecasts. The Company is required to adopt the new standard on January 1, 2020. Management is currently evaluating the potential impact that the adoption of this standard will have on the Company's financial position, results of operations, and related disclosures.
Revenue Recognition	The Company's revenues are primarily derived from consideration paid by customers to transfer money. These revenues vary by transaction based upon send and receive locations, the principal amount sent, whether the money transfer involves different send and receive currencies, the difference between the exchange rate set by the Company to the customer and the rate available in the wholesale foreign exchange market, speed of service, and channel, as applicable. The Company also offers several other services, including foreign exchange and payment services and other bill payment services, for which revenue is impacted by similar factors. When more than one party is involved in providing services to a customer, the Company generally acts as the principal in transactions and reports revenue on a gross basis, as the Company is primarily responsible for fulfilling the customer contracts, has the risk of loss, and has the ability to establish transaction prices. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities.
Earnings Per Share	The calculation of basic earnings per share is computed by dividing net income available to common stockholders by the weighted-average number of shares of common stock outstanding for the period. Outstanding options to purchase Western Union stock and unvested shares of restricted stock are excluded from basic shares outstanding. Diluted earnings per share reflects the potential dilution that could occur if outstanding stock options at the presented dates are exercised and shares of restricted stock have vested, using the treasury stock method. The treasury stock method assumes proceeds from the exercise price of stock options and the unamortized compensation expense of options and restricted stock are available to acquire shares at an average market price throughout the period, and therefore, reduce the dilutive effect.
Investment Securities	Investment securities included in "Settlement assets" in the Company's Condensed Consolidated Balance Sheets consist primarily of highly-rated state and municipal debt securities, including fixed rate term notes and variable rate demand notes. Variable rate demand note securities can be put (sold at par) typically on a daily basis with settlement periods ranging from the same day to one week, but have varying maturities through 2050. These securities may be used by the Company for short-term liquidity needs and held for short periods of time. The Company is required to hold highly-rated, investment grade securities and such investments are restricted to satisfy outstanding settlement obligations in accordance with applicable state and foreign country requirements. The substantial majority of the Company's investment securities are classified as available-for-sale and recorded at fair value. Investment securities are exposed to market risk due to changes in interest rates and credit risk. Western Union regularly monitors credit risk and attempts to mitigate its exposure by investing in highly-rated securities and through investment diversification. Unrealized gains and losses on available-for-sale securities are excluded from earnings and presented as a component of accumulated other comprehensive loss, net of related deferred taxes. Gains and losses on investments are calculated using the specific-identification method and are recognized during the period in which the investment is sold or when an investment experiences an other-than-temporary decline in value.
Foreign Currency — Derivatives	Foreign Currency Derivatives The Company's policy is to use longer-term foreign currency forward contracts, with maturities of up to 36 months at inception and a targeted weighted-average maturity of approximately one year, to help mitigate some of the risk that changes in foreign currency exchange rates compared to the United States dollar could have on forecasted revenues denominated in other currencies related to its business. As of June 30, 2018, the Company's longer-term foreign currency forward contracts had maturities of a maximum of 24 months with a weighted-average maturity of approximately one year. These contracts are accounted for as cash flow hedges of forecasted revenue, with effectiveness assessed based on changes in the spot rate of the affected currencies during the period of designation and thus time value is excluded from the assessment of effectiveness. As discussed in Note 1, the Company early adopted an accounting pronouncement related to hedging activities as of January 1, 2018. As a result of the new accounting pronouncement, for foreign currency cash flow hedges entered into on or after January 1, 2018, the Company excludes time value from the assessment of effectiveness, and the initial value of the excluded components is amortized into "Revenues" within the Company's Condensed Consolidated Statements of Income. For foreign currency cash flow hedges entered into before January 1, 2018, all changes in the fair value of the excluded components are recognized immediately in "Revenues" for the three and six months ended June 30, 2018. For the three and six months ended June 30, 2017, the changes in fair value of the excluded components were recognized immediately within the Company's Condensed Consolidated Statements of Income and are included in "Other income, net." The Company also uses short duration foreign currency forward contracts, generally with maturities from a few days up to one month, to offset foreign exchange rate fluctuations on settlement assets and obligations between initiation and settlement. In addition, forward contracts, typically with maturities of less than one year at inception, are utilized to offset foreign exchange rate fluctuations on certain foreign currency denominated cash and other asset and liability positions. None of these contracts are designated as accounting hedges.
Foreign Currency — Business Solutions Operations	Business Solutions Operations The Company writes derivatives, primarily foreign currency forward contracts and option contracts, mostly with small and medium size enterprises and derives a currency spread from this activity as part of its Business Solutions operations. The Company aggregates its Business Solutions foreign currency exposures arising from customer contracts, including the derivative contracts described above, and hedges the resulting net currency risks by entering into offsetting contracts with established financial institution counterparties (economic hedge contracts). The derivatives written are part of the broader portfolio of foreign currency positions arising from the Company's cross-currency payments operations, which primarily include spot exchanges of currency in addition to forwards and options. Foreign exchange revenues from the total portfolio of positions were $82.8 million and $85.9 million for the three months ended June 30, 2018 and 2017, respectively, and $168.6 million and $169.1 million for the six months ended June 30, 2018 and 2017, respectively. None of the derivative contracts used in Business Solutions operations are designated as accounting hedges. The duration of these derivative contracts at inception is generally less than one year.
Interest Rate Hedging	Interest Rate Hedging The Company utilizes interest rate swaps to effectively change the interest rate payments on a portion of its notes from fixed-rate payments to short-term LIBOR-based variable rate payments in order to manage its overall exposure to interest rates. The Company designates these derivatives as fair value hedges. The change in fair value of the interest rate swaps is offset by a change in the carrying value of the debt being hedged within "Borrowings" in the Condensed Consolidated Balance Sheets and "Interest expense" in the Condensed Consolidated Statements of Income has been adjusted to include the effects of interest accrued on the swaps. The Company, at times, utilizes derivatives to hedge the forecasted issuance of fixed-rate debt. These derivatives are designated as cash flow hedges of the variability in the fixed-rate coupon of the debt expected to be issued. The effective portion of the change in fair value of the derivatives is recorded in "Accumulated other comprehensive loss" in the Condensed Consolidated Balance Sheets.