Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Components of net periodic benefit cost
Contributions to qualified and non qualified pension plans				$ 3.5	$ 12.9
Pension Plan [Member]
Components of net periodic benefit cost
Service cost		$ 2.8	$ 0.9	4.6	2.7
Interest cost		7.1	5.9	19.5	17.8
Expected return on plan assets		(8.1)	(6.7)	(21.6)	(20.2)
Recognized net actuarial loss		1.5	1.7	4.3	5.0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments		(0.2)	0.0	(0.2)	0.0
Net periodic pension benefit cost		3.1	1.8	6.6	5.3
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Other Benefits [Member]
Components of net periodic benefit cost
Service cost		0.0	0.0	0.0	0.0
Interest cost		0.2	0.1	0.4	0.4
Expected return on plan assets		0.0	0.0	0.0	0.0
Recognized net actuarial loss		0.0	0.1	0.1	0.3
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments		0.0	0.0	0.0	0.0
Net periodic pension benefit cost		0.2	0.2	0.5	0.6
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		$ 0.0	$ 0.0	$ 0.0	$ (0.1)
Subsequent Event [Member]
Components of net periodic benefit cost
Contributions to qualified and non qualified pension plans	$ 2.0