Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue
Revenues from contracts with customers	$ 1,332.2		$ 4,039.5
Other revenues	55.6		148.8
Total revenues	1,387.8	$ 1,404.7	4,188.3	$ 4,086.0
North America
Disaggregation of Revenue
Revenues from contracts with customers	559.7		1,687.2
Europe and Russia/CIS
Disaggregation of Revenue
Revenues from contracts with customers	386.7		1,154.9
Middle East, Africa, and South Asia
Disaggregation of Revenue
Revenues from contracts with customers	158.6		491.0
Latin America and the Caribbean
Disaggregation of Revenue
Revenues from contracts with customers	134.6		422.9
East Asia and Oceania
Disaggregation of Revenue
Revenues from contracts with customers	92.6		283.5
Consumer money transfers
Disaggregation of Revenue
Revenues from contracts with customers	1,084.8		3,277.8
Other revenues	22.6		48.1
Total revenues	1,107.4		3,325.9
Consumer money transfers | North America
Disaggregation of Revenue
Revenues from contracts with customers	407.0		1,218.1
Consumer money transfers | Europe and Russia/CIS
Disaggregation of Revenue
Revenues from contracts with customers	349.4		1,051.1
Consumer money transfers | Middle East, Africa, and South Asia
Disaggregation of Revenue
Revenues from contracts with customers	157.8		489.7
Consumer money transfers | Latin America and the Caribbean
Disaggregation of Revenue
Revenues from contracts with customers	95.7		288.8
Consumer money transfers | East Asia and Oceania
Disaggregation of Revenue
Revenues from contracts with customers	74.9		230.1
Foreign exchange and payment services
Disaggregation of Revenue
Revenues from contracts with customers	80.0		227.7
Other revenues	20.2		62.3
Total revenues	100.2		290.0
Foreign exchange and payment services | North America
Disaggregation of Revenue
Revenues from contracts with customers	25.8		74.5
Foreign exchange and payment services | Europe and Russia/CIS
Disaggregation of Revenue
Revenues from contracts with customers	35.2		98.1
Foreign exchange and payment services | Middle East, Africa, and South Asia
Disaggregation of Revenue
Revenues from contracts with customers	0.7		1.0
Foreign exchange and payment services | Latin America and the Caribbean
Disaggregation of Revenue
Revenues from contracts with customers	1.0		2.0
Foreign exchange and payment services | East Asia and Oceania
Disaggregation of Revenue
Revenues from contracts with customers	17.3		52.1
Consumer bill payments
Disaggregation of Revenue
Revenues from contracts with customers	149.0		477.6
Other revenues	7.4		22.0
Total revenues	156.4		499.6
Consumer bill payments | North America
Disaggregation of Revenue
Revenues from contracts with customers	112.9		351.5
Consumer bill payments | Europe and Russia/CIS
Disaggregation of Revenue
Revenues from contracts with customers	0.9		2.5
Consumer bill payments | Middle East, Africa, and South Asia
Disaggregation of Revenue
Revenues from contracts with customers	0.1		0.3
Consumer bill payments | Latin America and the Caribbean
Disaggregation of Revenue
Revenues from contracts with customers	34.7		122.0
Consumer bill payments | East Asia and Oceania
Disaggregation of Revenue
Revenues from contracts with customers	0.4		1.3
Other services
Disaggregation of Revenue
Revenues from contracts with customers	18.4		56.4
Other revenues	5.4		16.4
Total revenues	23.8		72.8
Other services | North America
Disaggregation of Revenue
Revenues from contracts with customers	14.0		43.1
Other services | Europe and Russia/CIS
Disaggregation of Revenue
Revenues from contracts with customers	1.2		3.2
Other services | Middle East, Africa, and South Asia
Disaggregation of Revenue
Revenues from contracts with customers	0.0		0.0
Other services | Latin America and the Caribbean
Disaggregation of Revenue
Revenues from contracts with customers	3.2		10.1
Other services | East Asia and Oceania
Disaggregation of Revenue
Revenues from contracts with customers	$ 0.0		$ 0.0