Post Retirement Benefit Plans - Balance Sheet and AOCI (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Amounts recognized in the accompanying consolidated balance sheets:
Current liabilities	$ (1.6)	$ (2.1)
Non-current liabilities	(90.5)	(105.6)
Net amount recognized	(92.1)	(107.7)
Pre-tax amounts recognized in accumulated other comprehensive income:
Prior service cost	(6.9)	(9.7)
Net actuarial loss	(32.0)	(48.9)
Accumulated other comprehensive loss	(38.9)	(58.6)
Accumulated contributions below net periodic benefit cost	(53.2)	(49.1)
Net amount recognized	(92.1)	$ (107.7)
Accumulated other comprehensive income expected to be recognized as amortization of net loss within net periodic benefit cost in 2019	$ 1.9