Employee Benefits Schedule of Changes in Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period	$ 79.3
Fair value of plan assets, end of period	86.1	$ 79.3
Pension Plan and SERP [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of period	120.3	132.6
Service cost	1.2	2.1	$ 2.6
Interest cost	5.2	4.9	5.3
Loss on curtailment in current period	0.0	(7.1)
Benefit payments	(7.8)	(7.7)
Defined Benefit Plan, Plan Amendments	0.0	0.9
Actuarial loss (gain)	10.3	(5.4)
Benefit obligation, end of period	129.2	120.3	132.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period	79.3	81.4
Actual gain on plan assets	7.4	(1.9)
Company contributions to the plan	7.2	7.5
Benefit payments	(7.8)	(7.7)
Fair value of plan assets, end of period	86.1	79.3	81.4
Underfunded status (current and long-term)	(43.1)	(41.0)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Amounts included in accounts payable and accrued expenses	(2.5)	(2.9)
Amounts included in other long-term liabilities	(40.6)	(38.1)
Total amount recognized in balance sheets	(43.1)	(41.0)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial loss (gain)	23.5	15.8
Prior service cost	2.9	4.1
Total amount recognized in AOCI	26.4	19.9
Medical Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of period	5.2	6.6
Service cost	0.0	0.0	0.0
Interest cost	0.2	0.2	0.3
Loss on curtailment in current period	0.0	0.0
Benefit payments	(0.4)	(0.2)
Defined Benefit Plan, Plan Amendments	0.0	0.0
Actuarial loss (gain)	0.4	(1.4)
Benefit obligation, end of period	5.4	5.2	6.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period	0.0	0.0
Actual gain on plan assets	0.0	0.0
Company contributions to the plan	0.4	0.2
Benefit payments	(0.4)	(0.2)
Fair value of plan assets, end of period	0.0	0.0	$ 0.0
Underfunded status (current and long-term)	(5.4)	(5.2)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Amounts included in accounts payable and accrued expenses	(0.3)	(0.3)
Amounts included in other long-term liabilities	(5.1)	(4.9)
Total amount recognized in balance sheets	(5.4)	(5.2)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial loss (gain)	(0.4)	(0.8)
Prior service cost	1.0	1.2
Total amount recognized in AOCI	$ 0.6	$ 0.4