Investments in Unconsolidated Affiliates (Details) (USD $) In Millions	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Dec. 31, 2009
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	$ 458.6		$ 389.7
Symetra
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	456.7	421.0	387.5	416.1	372.5	307.7
Symetra | Common shareholders' equity
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	449.0	388.5	350.4	399.2	344.9	269.2
Symetra | Warrants
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	7.7	32.5	37.1	16.9	27.6	38.5
Pentelia Capital Management
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	$ 1.9		$ 2.2