Employee Benefits, Defined Benefit Plans Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
VEBA Postretirement Medical Obligations
Accrued annual contribution to VEBAs	$ 0.0		$ 19.6
VEBAs
VEBA Postretirement Medical Obligations
Accrued annual contribution to VEBAs			19.5
Union VEBA
VEBA Postretirement Medical Obligations
Accrued annual contribution to VEBAs			16.7
Accrued Veba contingent contribution - total	29.9
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments		$ 307.8
Income Tax Expense (Benefit)	$ 184.4	$ 184.4
Salaried VEBA
VEBA Postretirement Medical Obligations
Accrued annual contribution to VEBAs			$ 2.8