Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives - Changes in Liability Balances (Details) (Universal Life [Member], USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013
Universal Life [Member]
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability balance, beginning of the period	$ 300.4	$ 203.0	$ 328.7
Incurred	45.3	37.1
Liabilities for Guarantees on Long-Duration Contracts, Net Unrealized Gains (Losses) included in Accumulated Other Comprehensive Income	(17.0)	16.9
Assumption unlocking	$ 0	$ 43.4