Revenue Recognition Revenue Recognition - Services & Products (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues	$ 1,217.2	$ 1,285.1	$ 1,447.6
Investment revenue	20.0	54.7	49.5
Other Revenue
Revenues	52.8	51.5	47.9
Total Revenue from Services and Products
Revenues	1,144.4	1,178.9	1,350.2
Global Funds Transfer
Revenues	1,150.9	1,183.3	1,347.9
Global Funds Transfer | Money Transfer Fee Revenue
Revenues	1,083.4	1,102.1	1,255.4
Global Funds Transfer | Bill Payment Services Fee Revenue
Revenues	46.2	59.4	74.5
Global Funds Transfer | Other Revenue
Revenues	21.3	21.8	17.8
Global Funds Transfer | Total Global Funds Transfer Fee and Other Revenue
Revenues	1,150.9	1,183.3	1,347.7
Financial Paper Products
Revenues	66.3	101.8	99.7
Financial Paper Products | Other Revenue
Revenues	31.6	29.7	30.1
Financial Paper Products | Money Order Fee Revenue
Revenues	7.3	8.7	11.2
Financial Paper Products | Official Check Outsourcing Services Fee Revenue
Revenues	7.4	8.7	9.1
Financial Paper Products | Total Financial Paper Products Fee and Other Revenue
Revenues	46.3	47.1	50.4
Services and Products Transferred at a Point in Time
Revenues	1,137.0	1,170.2	1,341.1
Products Transferred Over Time
Revenues	$ 7.4	$ 8.7	$ 9.1