Financial Instruments - Fair Value on a Recurring Basis (Details) - Fair value measured on a recurring basis - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Plan assets for deferred compensation	$ 2.6	$ 3.2
Total assets	9.1	8.8
Liabilities
Plan liabilities for deferred compensation	2.6	3.2
Contingent consideration		2.9
Redeemable financial instrument	2.8
Total liabilities	5.4	6.1
Interest Rate Swaps
Assets
Derivative outstanding	6.5	5.6
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Plan assets for deferred compensation	2.6	3.2
Total assets	2.6	3.2
Liabilities
Plan liabilities for deferred compensation	2.6	3.2
Total liabilities	2.6	3.2
Significant Other Observable Inputs (Level 2)
Assets
Total assets	6.5	5.6
Significant Other Observable Inputs (Level 2) | Interest Rate Swaps
Assets
Derivative outstanding	6.5	5.6
Significant Unobservable Inputs (Level 3)
Liabilities
Contingent consideration		2.9
Redeemable financial instrument	2.8
Total liabilities	$ 2.8	$ 2.9