Derivative Financial Instruments (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Derivative Financial Instruments
Future potential payments in the event of default of an investment in fixed maturity securities that contain embedded credit derivatives	$ 0
Hybrid instruments disclosures
Amortized cost	87.9	74.6
Carrying value	86.7	73.2
Weighted average expected life	4 years 2 months 12 days	4 years
Corporate debt securities
Hybrid instruments disclosures
Amortized cost	23.4	23.4
Carrying value	23.4	23.4
Weighted average expected life	2 years 9 months 18 days	3 years
Corporate debt securities | A
Hybrid instruments disclosures
Amortized cost	23.4
Carrying value	23.4
Weighted average expected life	2 years 9 months 18 days
Corporate debt securities | BBB
Hybrid instruments disclosures
Amortized cost		23.4
Carrying value		23.4
Weighted average expected life		3 years
Structured finance
Hybrid instruments disclosures
Amortized cost	64.5	51.2
Carrying value	63.3	49.8
Weighted average expected life	4 years 8 months 12 days	4 years 6 months
Structured finance | A
Hybrid instruments disclosures
Amortized cost	30.6	18.1
Carrying value	29.4	16.7
Weighted average expected life	5 years 1 month 6 days	4 years 9 months 18 days
Structured finance | BB
Hybrid instruments disclosures
Amortized cost	5.6	5.5
Carrying value	5.6	5.5
Weighted average expected life	3 years 1 month 6 days	3 years 3 months 18 days
Structured finance | B
Hybrid instruments disclosures
Amortized cost	4.2	4.1
Carrying value	4.2	4.1
Weighted average expected life	3 years 1 month 6 days	3 years 1 month 6 days
Structured finance | CCC
Hybrid instruments disclosures
Amortized cost	24.1	23.5
Carrying value	$ 24.1	$ 23.5
Weighted average expected life	4 years 9 months 18 days	4 years 9 months 18 days