Accumulated Other Comprehensive Income (Loss) (Reconciliation Of The Components Of Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Investments, gross unrealized gains	$ 1,140.2	$ 1,003.0	$ 1,054.2
Investments, gross unrealized losses	(134.6)	(276.7)
Investments, net pretax unrealized gains	1,005.6	726.3
Deferred tax liability	(345.0)	(249.7)
Net unrealized gains on investments	660.6	476.6
Non-credit component of other than temporary impairments on investments, unrealized losses	(5.9)	(0.9)
Non-credit component of other than temporary impairments on investments, deferred tax asset	2.1	0.3
Net unrealized non-credit component of other than temporary impairments on investments	(3.8)	(0.6)
Cash flow hedges, gross unrealized losses	(56.5)	(50.8)
Cash flow hedges, deferred tax asset	19.8	17.8
Net unrealized losses on cash flow hedges	(36.7)	(33.0)
Defined benefit pension plans, deferred net actuarial loss	(424.2)	(654.0)
Defined benefit pension plans, deferred prior service credits	18.9	3.3
Defined benefit pension plans, deferred tax asset	162.3	256.4
Net unrecognized periodic benefit costs for defined benefit pension plans	(243.0)	(394.3)
Postretirement benefit plans, deferred net actuarial loss	(150.0)	(182.7)
Postretirement benefit plans, deferred prior service credits	79.0	93.2
Defined benefit pension plans, deferred tax asset	28.4	35.2
Net unrecognized periodic benefit costs for postretirement benefit plans	(42.6)	(54.3)
Foreign currency translation adjustments, gross unrealized gains (losses)	(2.1)	1.3
Foreign currency translation adjustments, deferred tax asset (liability)	0.7	(0.5)
Net unrealized (losses) gains on foreign currency translation adjustments	(1.4)	0.8
Accumulated other comprehensive income (loss)	$ 333.1	$ (4.8)	$ 183.2