Fair Value (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Impact on interest credited during the period due to changes in Level 3 actuarial assumptions	$ (1.5)	$ (1.4)	$ 2.2	$ (2.7)
Impaired recorded investment, with related allowance	73.5		73.5		$ 74.2
Assets measured at fair value on a nonrecurring basis during the period and still held as of the balance sheet date	59.3		59.3		66.3
Related Allowance	23.3	$ 24.6	23.3	$ 24.6	23.8
Real Estate Owned [Member]
Capital losses recorded during the period on real estate owned measured on a nonrecurring basis and still held			0.8		1.2
Assets measured at fair value on a nonrecurring basis during the period and still held as of the balance sheet date	3.5		3.5		10.3
Commercial Mortgage Loans [Member]
Assets measured at fair value on a nonrecurring basis during the period and still held as of the balance sheet date	$ 55.8		$ 55.8		$ 56.0