Investments in Unconsolidated Affiliates (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	$ 414.4	$ 321.4
Symetra
Investments in unconsolidated affiliates
Unrealized gains (losses) from Symetra’s fixed maturity portfolio	37.6	(43.6)
Investments in unconsolidated affiliates	411.4	317.3	381.5	273.6
Symetra | Common Stock
Investments in unconsolidated affiliates
Symetra common shares	373.8	360.9
Investments in unconsolidated affiliates	411.4	317.3	351.2	261.0
Symetra | Warrants
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	0	0	30.3	12.6
Hamer, LLC
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	$ 3.0	$ 4.1