Investments (Schedule Of Contractual Maturities Of Fixed Maturity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Investments [Abstract]
Due in one year or less, Amortized cost	$ 595.4	$ 649.0
Due after one year through five years, Amortized cost	3,039.9	3,060.8
Due after five years through ten years, Amortized Cost	2,955.6	2,847.9
Due after ten years, Amortized Cost	840.6	832.3
Total fixed maturity securities-available-for-sale, Amortized Cost	7,431.5	7,390.0
Due in one year or less, Fair Value	605.4	658.0
Due after one year through five years, Fair Value	3,204.6	3,215.4
Due after five years through ten years, Fair Value	3,067.8	2,916.7
Due after ten years, Fair Value	1,007.9	983.6
Total fixed maturity securities-available-for-sale	$ 7,885.7	$ 7,773.7