Investments (Details 4) (USD $) In Millions, unless otherwise specified		3 Months Ended														3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Fixed maturity investments	Mar. 31, 2013 Fixed maturity investments	Mar. 31, 2014 Equity investments	Mar. 31, 2013 Equity investments	Mar. 31, 2014 Recurring basis Level 3	Mar. 31, 2013 Recurring basis Level 3	Mar. 31, 2014 Recurring basis Level 3 Fixed maturity investments	Mar. 31, 2013 Recurring basis Level 3 Fixed maturity investments	Mar. 31, 2014 Recurring basis Level 3 Corporate debt securities	Mar. 31, 2013 Recurring basis Level 3 Corporate debt securities	Mar. 31, 2014 Recurring basis Level 3 Other debt obligations	Mar. 31, 2013 Recurring basis Level 3 Other debt obligations	Mar. 31, 2014 Recurring basis Level 3 Equity investments	Dec. 31, 2013 Recurring basis Level 3 Equity investments	Mar. 31, 2014 Recurring basis Level 3 Other investments	Mar. 31, 2013 Recurring basis Level 3 Other investments
Reconciliations of the beginning and ending balances for all investments measured at fair value on a recurring basis using Level 3 inputs
Beginning Level 3 balance						$ 28.6	$ 124.3	$ 28.3	$ 111.6	$ 10.0	$ 95.4	$ 18.3	$ 16.2	$ 0.2	$ 0.2	$ 0.1	$ 12.7
Purchases						5.0	27.2	5.0	27.2	0.8	7.7	4.2	19.5
Sales and maturities						(7.7)	(40.7)	(7.6)	(29.8)	(2.4)	(25.3)	(5.2)	(4.5)			(0.1)	(10.9)
Net realized gains (loss)						0.2	(2.2)	0.2	(4.2)	0.1	(4.2)	0.1					2.0
Net unrealized gains (losses)		18.8	(14.5)	0.7	0.8		8.2		10.8	(0.1)	10.4	0.1	0.4				(2.6)
Net transfers						(1.7)	(93.7)	(1.7)	(93.7)	(0.3)	(80.9)	(1.4)	(12.8)
Ending Level 3 balance						24.4	23.1	24.2	21.9	8.1	3.1	16.1	18.8	0.2	0.2		1.2
Transfers out of Level 3 of fair value hierarchy	$ 0