Retirement Plans (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Defined Contribution Plans
Defined contribution plan expense recognized	$ 4.1	$ 3.6
Maximum percentage of employee compensation match by employer to employee stock ownership plan	4.00%
Maximum percentage of employee compensation match by employer to non union employee stock ownership plan	50.00%
Shares held by the ESOP plan	1.3		1.3
Defined Benefit Plans
Components of net periodic benefit cost
Service cost	$ 0.8	0.9
Interest cost	1.3	1.8
Expected return on plan assets	(2.5)	(2.6)
Amortization of unrecognized loss	0.6	1.3
Net periodic benefit cost	$ 0.2	$ 1.4