Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of Net Periodic Benefit Cost (Income) [Abstract]
Employer Contributions to Defined Benefit Pension Plans - Cash			$ 1.7	$ 0.0
Employer Contributions to Defined Benefit Pension Plans - Common Stock Value			13.5	0.0
Pension [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service Cost	$ 2.6	$ 2.1	5.1	4.1
Interest Cost	8.2	8.1	16.3	16.2
Expected Return on Plan Assets	(10.6)	(10.7)	(21.2)	(21.3)
Amortization of Prior Service Credits	0.0	0.0	0.0	0.0
Amortization of Net Loss	2.4	2.5	4.9	4.9
Net Periodic Benefit Cost (Income)	2.6	2.0	5.1	3.9
Employer Contributions to Defined Benefit Pension Plans - Cash			1.7
Employer Contributions to Defined Benefit Pension Plans - Common Stock Value			13.5
Employer Contributions to Defined Benefit Plans				0.0
Expected Future Employer Contributions in 2017			0.0
Other Postretirement [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service Cost	1.1	1.0	2.2	2.0
Interest Cost	1.9	1.8	3.8	3.7
Expected Return on Plan Assets	(2.7)	(2.8)	(5.3)	(5.6)
Amortization of Prior Service Credits	(0.5)	(0.8)	(1.0)	(1.5)
Amortization of Net Loss	0.1	0.1	0.2	0.1
Net Periodic Benefit Cost (Income)	$ (0.1)	$ (0.7)	(0.1)	(1.3)
Employer Contributions to Defined Benefit Plans			0.0	$ 0.0
Expected Future Employer Contributions in 2017			$ 0.0