Fair Value Of Assets And Liabilities (Fair Value Of Financial Instruments Held By Consolidated Investments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,514.2	$ 1,331.2	$ 835.5	$ 727.4
Available for sale investments	255.9	244.1
Foreign time deposits	29.6	28.8
Assets held for policyholders	1,697.9	1,416.0
Policyholder payables	(1,697.9)	(1,416.0)
Long-term debt	(1,589.3)	(1,588.6)
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,514.2	1,331.2
Available for sale investments	255.9	244.1
Trading investments	263.2	253.0
Foreign time deposits	29.6	28.8
Assets held for policyholders	1,697.9	1,416.0
Policyholder payables	(1,697.9)	(1,416.0)
Financial instruments sold, not yet purchased	(1.4)	(1.7)
Note payable	0	(0.3)
Long-term debt	(1,589.3)	(1,588.6)
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,514.2	1,331.2
Available for sale investments	255.9	244.1
Trading investments	263.2	253.0
Foreign time deposits	29.6	28.8
Assets held for policyholders	1,697.9	1,416.0
Policyholder payables	(1,697.9)	(1,416.0)
Financial instruments sold, not yet purchased	(1.4)	(1.7)
Note payable	0	(0.3)
Long-term debt	$ (1,695.8)	$ (1,544.7)