Derviative Financial Instruments (Details 4) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Hybrid instruments disclosures
Amortized cost	$ 111.1	$ 110.9
Carrying value	108.2	99.7
Weighted average expected life	3 years 6 months	3 years 10 months 24 days
Corporate debt securities
Hybrid instruments disclosures
Amortized cost	44.0	43.4
Carrying value	43.4	36.2
Weighted average expected life	2 years 3 months 18 days	2 years 10 months 24 days
Corporate debt securities | BBB
Hybrid instruments disclosures
Amortized cost	19.0
Carrying value	19.0
Weighted average expected life	4 years 3 months 18 days
Corporate debt securities | BB
Hybrid instruments disclosures
Amortized cost		14.7
Carrying value		14.7
Weighted average expected life		5 years
Corporate debt securities | B
Hybrid instruments disclosures
Amortized cost	25.0
Carrying value	24.4
Weighted average expected life	9 months 18 days
Corporate debt securities | CCC
Hybrid instruments disclosures
Amortized cost		25.0
Carrying value		20.8
Weighted average expected life		1 year 6 months
Corporate debt securities | CC
Hybrid instruments disclosures
Amortized cost		3.7
Carrying value		0.7
Weighted average expected life		4 years
Structured finance
Hybrid instruments disclosures
Amortized cost	67.1	67.5
Carrying value	64.8	63.5
Weighted average expected life	4 years 4 months 24 days	4 years 6 months
Structured finance | AA
Hybrid instruments disclosures
Amortized cost	6.4	9.3
Carrying value	6.4	9.3
Weighted average expected life	7 years 6 months	6 years 4 months 24 days
Structured finance | BBB
Hybrid instruments disclosures
Amortized cost		27.4
Carrying value		24.5
Weighted average expected life		4 years 6 months
Structured finance | BB
Hybrid instruments disclosures
Amortized cost	43.5	15.0
Carrying value	40.7	13.9
Weighted average expected life	3 years 2 months 12 days	2 years 6 months
Structured finance | B
Hybrid instruments disclosures
Amortized cost		11.2
Carrying value		11.2
Weighted average expected life		5 years 4 months 24 days
Structured finance | CCC
Hybrid instruments disclosures
Amortized cost	16.9	3.5
Carrying value	17.4	3.6
Weighted average expected life	5 years 10 months 24 days	4 years 9 months 18 days
Structured finance | CC
Hybrid instruments disclosures
Amortized cost	0.3	0.7
Carrying value	0.3	0.7
Weighted average expected life	19 years 4 months 24 days	5 years 3 months 18 days
Structured finance | C
Hybrid instruments disclosures
Amortized cost		0.2
Carrying value		0.1
Weighted average expected life	4 years 2 months 12 days	8 years 2 months 12 days
Structured finance | Near default
Hybrid instruments disclosures
Amortized cost		0.2
Carrying value		$ 0.2
Weighted average expected life		4 years 8 months 12 days