Accumulated Other Comprehensive Loss Reclassification Adjustments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Interest Expense		$ 7.6	$ 7.9	$ 15.6	$ 14.8
Unrealized loss on securities (net of tax $0.0, $0.2, $0.0 and $0.2, respectively)		6.8	10.0	14.7	18.7
Total reclassifications for the period		1.1	0.0	2.1	0.4
Interest Rate Hedges
Total reclassifications for the period		0.0	0.0	(0.1)	(0.1)
Interest Rate Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest Expense		0.0	0.0	(0.1)	(0.1)
Net actuarial loss amortization (net of tax $(0.6), $(0.3), $(1.2) and $(0.6), respectively) | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net periodic benefit cost	[1]	(1.2)	(0.5)	(2.3)	(1.0)
Net prior service benefit amortization | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net periodic benefit cost	[1]	(0.1)	(0.1)	(0.1)	(0.1)
Pension and Other Post-retirement Benefits
Total reclassifications for the period		1.1	0.4	2.2	0.9
Pension and Other Post-retirement Benefits | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net periodic benefit cost		1.1	0.4	2.2	0.9
Net actuarial loss amortization, tax		(0.6)	(0.3)	(1.2)	(0.6)
Unrealized loss on securities | Reclassification out of Accumulated Other Comprehensive Income [Member]
Unrealized loss on securities (net of tax $0.0, $0.2, $0.0 and $0.2, respectively)		$ 0.0	$ 0.4	$ 0.0	$ 0.4

[1] Pension and other post-retirement benefits AOCI components are included in the computation of net periodic benefit cost (refer to note 12).