Post Retirement Benefit Plans - Balance Sheet and AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the accompanying consolidated balance sheets:
Current liabilities	$ (1.7)	$ (1.5)
Non-current liabilities	(102.5)	(91.6)
Net amount recognized	(104.2)	(93.1)
Pre-tax amounts recognized in accumulated other comprehensive income:
Prior service cost	(10.6)	(12.2)
Net actuarial loss	(56.0)	(48.5)
Accumulated other comprehensive loss	(66.6)	(60.7)
Accumulated contributions in excess of net periodic benefit cost	(37.6)	(32.4)
Net amount recognized	(104.2)	$ (93.1)
Accumulated other comprehensive income expected to be recognized as amortization of net loss within net periodic benefit cost in 2017	$ 4.6