Other Assets - Other Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Other Assets
Right-of-use lease asset	$ 233.1	$ 0.0
Deferred compensation plan	107.1	100.0
Deferred contract costs and sales commissions	84.4	89.2
Reinsurance receivable	77.7	68.0
Investments	63.3	73.0
Prepaid fees and capitalized implementation costs for cloud-based hosting arrangements	39.2	0.0
Amounts recoverable for capping, closure and post-closure obligations	32.1	30.5
Interest rate swaps and locks	11.6	12.8
Deferred financing costs	3.6	4.2
Other	34.3	40.1
Total	$ 686.4	$ 417.8