Other Assets - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Prepaid Expenses and Other Current Assets
Income tax receivable	$ 105.3	$ 187.7
Prepaid expenses	72.7	75.6
Inventories	55.4	53.1
Reinsurance receivable	29.9	25.7
Other non-trade receivables	25.7	34.4
Prepaid fees for cloud-based hosting arrangements, current	9.9	10.2
Other current assets	4.0	4.5
Total	$ 302.9	$ 391.2