Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in the carrying amount of goodwill
Balance at the beginning of the year	$ 1,870.8	$ 1,842.6	$ 1,827.4
Acquisitions	131.8	33.8	10.3
Purchase price allocation adjustments	(1.9)
Foreign currency translation gains (losses)	3.1	(5.6)	4.9
Balance at the end of the year	2,003.8	$ 1,870.8	$ 1,842.6
Accumulated impairment losses	0.0
Goodwill, tax deductible amount	817.4
2019 Acquisitions
Change in the carrying amount of goodwill
Goodwill, tax deductible amount	$ 131.0