Other Comprehensive Income (Reconciliation Of Gross Unrealized Investment Gains) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Other Comprehensive Income [Abstract]
Unrealized gains arising during period, Pre-Tax	$ 70.5	$ 6.4
Unrealized gains arising during period, Tax Benefit (Expense)	(21.0)	5.2
Unrealized gains arising during period, Net of Tax	49.5	11.6
Less: reclassification adjustments for gains realized in net income, Pre-Tax	2.3	2.9
Less: reclassification adjustments for gains realized in net income, Tax Benefit (Expense)	3.3	2.1
Less: reclassification adjustments for gains realized in net income, Net of Tax	5.6	5.0
Total available-for-sale securities, Pre-Tax	68.2	3.5
Total available-for-sale securities, Tax Benefit (Expense)	(24.3)	3.1
Total available-for-sale securities	$ 43.9	$ 6.6