Investments in Unconsolidated Affiliates (Symetra) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 20, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2012
Investments in unconsolidated affiliates
Common shares received from exercised warrants			$ 2.65
Average price per share	$ 600.00	$ 508.00		$ 564.00	$ 497.00
Symetra
Investments in unconsolidated affiliates
Shares of Symetra Financial Corporation owned (in shares)	20,050,000			20,050,000			17,400,000
Ownership interest (as a percent)	17.00%			17.00%			15.00%
Investments in unconsolidated affiliates on conversion of warrants	9,490,000		9,490,000	9,490,000
Unamortized basis difference			19.3
Fair value of investment						261.0
Estimated fair value of investment per share						$ 15
Impairment of Common Shares Equity in Earnings after Tax						45.9
Equity in net unrealized losses increase relating to amortization of common share impairment						136.6
Term of amortization (in years)				30 years
After tax amortization through equity in earnings	0.7			1.4
After tax amortization through equity in net unrealized losses	2.5			5.0
Pre-tax unamortized basis difference	191.5			191.5
Gain (Loss) on Warrants	14.5	6.1		10.8	17.2
Risk free interest rate (as a percent)			0.34%
Volatility rate (as a percent)			26.50%
Expected life (in years)			1 year 1 month 10 days
Class of warrant or right fair value assumptions per strike price			$ 11.49
Market Price Per Share	$ 15.99		$ 15.53	$ 15.99
Proceeds from Equity Method Investment, Dividends or Distributions	(1.4)	(1.2)		(2.8)	(2.4)
Common Stock | Symetra
Investments in unconsolidated affiliates
Equity in net unrealized losses increase relating to amortization of common share impairment	2.8	3.3		5.5	6.6
Gain (Loss) on Warrants	0	0		0	0
Proceeds from Equity Method Investment, Dividends or Distributions	(1.4)	(1.2)		(2.8)	(2.4)
Warrants | Symetra
Investments in unconsolidated affiliates
Gain (Loss) on Warrants	14.5	6.1		10.8	17.2
Proceeds from Equity Method Investment, Dividends or Distributions	0	0		0	0
Proceeds from Dividends Received	0.7			1.5
Symetra
Investments in unconsolidated affiliates
Stock Repurchased and Retired During Period, Shares				6,600,000
Average price per share			$ 13.44
Income (Loss) from Equity Method Investments [Member] | Symetra
Investments in unconsolidated affiliates
Unamortized basis difference			0.4
Pre-tax unamortized basis difference	40.5			40.5
Net unrealized gains (losses) of unconsolidated affiliates [Member] | Symetra
Investments in unconsolidated affiliates
Unamortized basis difference			18.9
Pre-tax unamortized basis difference	$ 151.0			$ 151.0