Other Assets (Other Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Other Assets
Operating right-of-use lease assets	$ 255.3	$ 218.8
Deferred compensation plan	133.5	131.8
Investments	127.6	145.4
Deferred contract costs and sales commissions	80.6	82.3
Reinsurance receivable	79.5	84.8
Prepaid fees and capitalized implementation costs for cloud-based hosting arrangements	43.4	29.5
Amounts recoverable for capping, closure and post-closure obligations	19.4	18.5
Other derivative assets	15.0	63.8
Deferred financing costs	4.6	2.7
Interest rate swaps	4.7	10.0
Other	24.0	29.8
Total	$ 787.6	$ 817.4
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Total	Total