Intangible Assets and Goodwill - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Changes in carrying amount of goodwill
Balance at the beginning of the period	$ 516.4	$ 458.3
Acquisitions	265.4	61.0
Impairments	0.0	0.0
Other	17.3	(2.9)
Balance at the end of the period	799.1	516.4
Domestic Financial Services
Changes in carrying amount of goodwill
Balance at the beginning of the period	345.8	286.5
Acquisitions	68.7	61.0
Impairments	0.0	0.0
Other	0.9	(1.7)
Balance at the end of the period	415.4	345.8
International Financial Services
Changes in carrying amount of goodwill
Balance at the beginning of the period	15.6	16.8
Acquisitions	196.7	0.0
Impairments	0.0	0.0
Other	16.4	(1.2)
Balance at the end of the period	228.7	15.6
Healthcare Services
Changes in carrying amount of goodwill
Balance at the beginning of the period	155.0	155.0
Acquisitions	0.0	0.0
Impairments	0.0	0.0
Other	0.0	0.0
Balance at the end of the period	$ 155.0	$ 155.0