Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Components of Net Periodic Benefit Expense (Income) [Abstract]
Employer Contributions to Defined Benefit Pension Plan - Cash	$ 1.7	$ 0.0
Employer Contributions to Defined Benefit Pension Plan - Common Stock Value	13.5	0.0
Pension [Member]
Components of Net Periodic Benefit Expense (Income) [Abstract]
Service Cost	2.5	2.0
Interest Cost	8.1	8.1
Expected Return on Plan Assets	(10.6)	(10.6)
Amortization of Prior Service Credits	0.0	0.0
Amortization of Net Loss	2.5	2.4
Net Periodic Benefit Expense (Income)	2.5	1.9
Employer Contributions to Defined Benefit Pension Plan - Cash	1.7
Employer Contributions to Defined Benefit Pension Plan - Common Stock Value	13.5
Employer Contributions to Defined Benefit Plan		0.0
Expected Future Employer Contributions in 2017	0.0
Other Postretirement [Member]
Components of Net Periodic Benefit Expense (Income) [Abstract]
Service Cost	1.1	1.0
Interest Cost	1.9	1.9
Expected Return on Plan Assets	(2.6)	(2.8)
Amortization of Prior Service Credits	(0.5)	(0.7)
Amortization of Net Loss	0.1	0.0
Net Periodic Benefit Expense (Income)	0.0	(0.6)
Employer Contributions to Defined Benefit Plan	0.0	$ 0.0
Expected Future Employer Contributions in 2017	$ 0.0