Other Assets - Other Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Assets
Operating lease assets	$ 228.0	$ 0.0
Deferred compensation plan	107.8	100.0
Deferred contract costs and sales commissions	87.0	89.2
Reinsurance receivable	77.8	68.0
Investments	61.4	73.0
Prepaid fees and capitalized implementation costs for cloud-based hosting arrangements	35.8	0.0
Amounts recoverable for capping, closure and post-closure obligations	31.2	30.5
Interest rate swaps and locks	13.3	12.8
Deferred financing costs	3.9	4.2
Other	39.7	40.1
Total	$ 685.9	$ 417.8