Employee Benefit Plans - Change in Level 3 Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 104.5
Fair value of assets at end of year	99.3	$ 104.5
Level 3
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	12.9	12.5
Unrealized gain (loss) on asset still held	(2.0)	0.4
Fair value of assets at end of year	$ 10.9	$ 12.9