Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2015	Nov. 05, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments in and Advances to Affiliates [Line Items]
Investments in unconsolidated affiliates	$ 0.0	$ 392.8	$ 414.4
Symetra
Investments in and Advances to Affiliates [Line Items]
Unrealized (losses) gains from Symetra’s fixed maturity portfolio		(1.6)	37.6
Investments in unconsolidated affiliates		392.8	411.4	$ 317.3	$ 381.5
Symetra | Common Stock
Investments in and Advances to Affiliates [Line Items]
Symetra common shares		394.4	373.8
Investments in unconsolidated affiliates		392.8	411.4	317.3	351.2
Symetra | Warrants
Investments in and Advances to Affiliates [Line Items]
Investments in unconsolidated affiliates		0.0	0.0	$ 0.0	$ 30.3
Hamer, LLC
Investments in and Advances to Affiliates [Line Items]
Investments in unconsolidated affiliates		$ 0.0	$ 3.0