Pension and Postretirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Capitalized portion of defined benefit contribution percent	10.00%	10.00%
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			$ 2.0
Pension and Other Postretirement Benefit Contributions	$ 0.6
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.0	$ 0.0
Interest cost on projected benefit obligation	4.8	4.6
Expected return on plan assets	(6.8)	(7.2)
Amortization of:
Prior service cost (benefit)	0.0	0.1
Actuarial loss	4.8	5.1
Total amortization	4.8	5.2
Benefit costs	2.8	2.6
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			$ 10.0
Pension and Other Postretirement Benefit Contributions	1.9
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.1	0.1
Interest cost on projected benefit obligation	0.8	0.8
Expected return on plan assets	0.0	0.0
Amortization of:
Prior service cost (benefit)	(3.7)	(3.9)
Actuarial loss	1.2	1.4
Total amortization	(2.5)	(2.5)
Benefit costs	$ (1.6)	$ (1.6)