Investments in Unconsolidated Affiliates (Symetra Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				6 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 20, 2013
Investments in unconsolidated affiliates
Common shares repurchased and retired during the period		1,329,640
Treasury Stock Acquired, Average Cost Per Share	$ 617.00	$ 564.00	$ 503.00
Symetra
Investments in unconsolidated affiliates
Shares of symetra financial corporation owned (in shares)	20,050,000
Ownership interest (as a percent)	17.31%	17.03%
Dividends received	$ (34.1)	$ (6.4)	$ (4.9)
Investments in unconsolidated affiliates on conversion of warrants			9,490,000		2,650,000
Gain (Loss) on Warrants		10.8	17.7
Fair value of investment				261.0
Estimated fair value of investment per share				$ 15
After-tax equity in losses of unconsolidated affiliates				45.9
Equity in net unrealized losses increase relating to amortization of common share impairment				136.6
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	2.4				19.3
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Attributable to Equity Earnings in Affiliates	0.5
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Net Unrealized Gains and Losses of Affiliate	1.9
Term of amortization (in years)			30 years
Weight Average Years Remaining	28 years
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Unamortized Basis Difference Attributable to Equity Earnings	36.4
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Unamortized Basis Difference Attributable to Unrealized Gains in Affiliates	134.0
Common Stock | Symetra
Investments in unconsolidated affiliates
Dividends received	(34.1)	(6.4)	(4.9)
Per share price, class of warrant (in dollars per share)	$ 23.05
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
Per share price, class of warrant (in dollars per share)			$ 11.49
Gain (Loss) on Warrants		10.8	17.7
Cash dividends received on warrants					1.5
Symetra | Common Stock
Investments in unconsolidated affiliates
Common shares repurchased and retired during the period					6,600,000
Treasury Stock Acquired, Average Cost Per Share					$ 13.44
equity in earnings of unconsolidated affiliates [Member] | Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	170.4				0.4
After tax amortization through equity in earnings	2.8
Net unrealized gains (losses) of unconsolidated affiliates [Member] | Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity					18.9
After tax amortization through equity in net unrealized losses	$ 11.7