Investments in Unconsolidated Affiliates (Symetra Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	6 Months Ended	10 Months Ended	12 Months Ended
	Feb. 01, 2016	Dec. 31, 2015	Jun. 30, 2013	Nov. 05, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 20, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments in unconsolidated affiliates
Trading Securities, Change in Unrealized Holding Gain (Loss)					$ 152.9	$ (79.3)	$ 40.3
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax					140.6	(69.4)	43.6
After tax amortization through equity in net unrealized losses					(36.3)	75.3	(98.1)
Sales of common equity securities					$ 461.4	$ 609.8	435.0
Common shares, par value per share (in dollars per share)		$ 1.00			$ 1.00	$ 1.00
Symetra
Investments in unconsolidated affiliates
Trading Securities, Change in Unrealized Holding Gain (Loss)		$ 258.8
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax		$ 241.1
Stock Dividends, Shares					513,500
Shares of symetra financial corporation owned (in shares)				20,562,379		20,048,879
Ownership interest (as a percent)				17.70%		17.31%
Dividends received				$ (16.9)		$ (34.1)	$ (6.4)
Investments in unconsolidated affiliates on conversion of warrants							9,490,000	2,650,000	9,490,000
Gain (Loss) on Warrants							$ 10.8
Fair value of investment										$ 261.0
Estimated fair value of investment per share										$ 15
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				159.9		170.4
Term of amortization (in years)					30 years
Common Stock | Symetra
Investments in unconsolidated affiliates
Dividends received				$ (16.9)		(34.1)	(6.4)
Per share price, class of warrant (in dollars per share)				$ 31.67
Gain (Loss) on Warrants							0.0
Warrants
Investments in unconsolidated affiliates
Gain (Loss) on Warrants			$ 10.8
Warrants | Symetra
Investments in unconsolidated affiliates
Dividends received				$ 0.0		0.0	$ 0.0
Per share price, class of warrant (in dollars per share)							$ 11.49
Gain (Loss) on Warrants							$ 10.8
Cash dividends received on warrants			$ 1.5
equity in earnings of unconsolidated affiliates [Member] | Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				32.6		36.4
After tax amortization through equity in earnings				2.2		2.8	2.7
Net unrealized gains (losses) of unconsolidated affiliates [Member] | Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				127.3		134.0
After tax amortization through equity in net unrealized losses				$ 8.9		$ 11.7	$ 10.8
Subsequent Event [Member] | Symetra
Investments in unconsolidated affiliates
Sales of common equity securities	$ 658.0
Common shares, par value per share (in dollars per share)	$ 32.00