| Cover | Nov. 25, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 25, 2019 |
| Entity File Number | 001-32903 |
| Entity Registrant Name | Western Union CO |
| Entity Central Index Key | 0001365135 |
| Entity Tax Identification Number | 20-4531180 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 7001 East Belleview Avenue |
| Entity Address, City or Town | Denver |
| Entity Address, State or Province | CO |
| Entity Address, Postal Zip Code | 80237 |
| City Area Code | 866 |
| Local Phone Number | 405-5012 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 Par Value |
| Trading Symbol | WU |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
