Contingencies, Commitments and Leases Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Leases, Capital [Abstract]
New headquarters building lease term	17 years
Commencement date of capital lease on new headquarters building	May 01, 2012
Description of Lessee Leasing Arrangements, Capital Leases	Rental payments under the lease escalate at a rate of 3% per year during the lease term. The lease agreement does not include bargain renewal periods or material rent holidays and is not subject to contingent rent or other unusual provisions.
Assets under capital lease included in other property, plant and equipment	$ 40.8	$ 40.8
Assets under capital lease included in other accumulated depreciation, depletion and amortization	9.1	6.7
Current capital lease obligation	1.2	1.0
Noncurrent capital lease obligation	36.0	$ 37.4
Future minimum payments and present value of net minimum payments under capital lease [Abstract]
2016	3.2
2017	3.6
2018	3.7
2019	3.8
2020	3.9
After 2020	37.2
Total minimum lease payments	55.4
Less: amount representing interest	(18.2)
Present value of minimum lease payments at year-end	$ 37.2