Investments in Unconsolidated Affiliates (Symetra) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended					0 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Symetra	Sep. 30, 2014 Symetra	Dec. 31, 2011 Symetra	Dec. 31, 2013 Symetra	Jun. 20, 2013 Symetra	Sep. 30, 2014 Common Stock Symetra	Dec. 31, 2011 Common Stock Symetra	Jun. 20, 2013 Warrants Symetra	Jun. 20, 2014 Warrants Symetra	Jun. 20, 2013 Symetra Common Stock	Sep. 30, 2014 equity in earnings of unconsolidated affiliates Symetra	Jun. 20, 2013 equity in earnings of unconsolidated affiliates Symetra	Sep. 30, 2014 Net unrealized gains (losses) of unconsolidated affiliates Symetra	Jun. 20, 2013 Net unrealized gains (losses) of unconsolidated affiliates Symetra
Investments in unconsolidated affiliates
Shares of Symetra Financial Corporation owned (in shares)				20,050,000	20,050,000		20,050,000
Ownership interest (as a percent)				17.30%	17.30%		17.00%
Investments In Unconsolidated Affiliates On Conversion Of Warrants								9,490,000
Common shares received from exercised warrants								2,650,000
Stock Repurchased and Retired During Period, Shares													6,600,000
Average price per share	$ 626.13	$ 614.78	$ 564.00										$ 13.44
Unamortized basis difference								$ 19.3							$ 0.4		$ 18.9
Fair value of investment										261.0
Term of amortization (in years)						30 years
Weight Average Years Remaining					27 years
After tax amortization through equity in earnings				0.7	2.1
After tax amortization through equity in net unrealized losses				2.9	8.7
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				174.0	174.0
Pre-tax unamortized basis difference														$ 36.9		$ 137.1
Expected life (in years)											1 year 1 month 10 days
Class of warrant or right fair value assumptions per strike price												11.49
Fair Value Assumptions, Risk Free Interest Rate											0.34%
Fair Value Assumptions, Expected Volatility Rate											26.50%
Share Price									$ 22.70			$ 15.53