New Accounting Pronouncements - Leases (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 155.0
Operating lease, liability	165.2
Retained earnings	7,576.8		$ 7,692.9
Current finance lease liabilities	33.9
Non-current finance lease liabilities	$ 50.9
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 154.0
Operating lease, liability		164.0
Retained earnings		32.0
Current finance lease liabilities		3.0
Non-current finance lease liabilities		$ 82.0