Employee Benefit Plans - Amounts recognized in accumulated other comprehensive income (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Pension Plans
Employee benefit plans
Net actuarial gain (loss)	$ (113.5)	$ (128.5)
Prior service credit	(0.7)	(0.8)
Total amount recognized	(114.2)	(129.3)
Postretirement Health and Other
Employee benefit plans
Net actuarial gain (loss)	(3.8)	(5.8)
Prior service credit	0.0	0.0
Total amount recognized	$ (3.8)	$ (5.8)