Pension Plans and Other Postretirement Benefit Plans - Pension Plans and Other Postretirement Benefit (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Funded status of fully funded, underfunded, and unfunded pension plans:
Underfunded and unfunded defined benefit pension plans	$ 452.1	$ 424.3
Pension liabilities included in other current liabilities	15.3	14.4
Net funded status	(467.4)	(438.7)
Unfunded defined benefit pension plans [Member]
Funded status of fully funded, underfunded, and unfunded pension plans:
Underfunded and unfunded defined benefit pension plans	371.7	341.2
Underfunded defined benefit pension plans [Member]
Funded status of fully funded, underfunded, and unfunded pension plans:
Underfunded and unfunded defined benefit pension plans	$ 80.4	$ 83.1