Employee Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of Net Retirement Cost
Service cost	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Interest	4.9	5.2	9.8	10.4
Expected return on plan assets	(6.8)	(6.8)	(13.6)	(13.6)
Amortization of actuarial loss	1.2	1.3	2.4	2.6
Defined benefit expense	(0.6)	(0.2)	(1.2)	(0.4)
Profit sharing	3.8	3.9	7.8	8.5
Multiemployer plan	0.4	0.6	1.0	1.2
Net expense	$ 3.6	$ 4.3	$ 7.6	$ 9.3