Investments in Unconsolidated Affiliates (Details 2) (Symetra, USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended	3 Months Ended
	Dec. 31, 2011 technic representative Y	Dec. 31, 2011 Minimum	Dec. 31, 2011 Maximum	Jan. 31, 2010 Initial public offering	Mar. 31, 2010 Initial public offering
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates (in shares)	17,400,000
Additional common shares (in shares)	9,500,000
Initial public offering issue price (in dollars per share)				$ 12.00
Sale of Symetra common shares by Symetra (in shares)				25,300,000
Sale of Symetra common shares by existing shareholders (in shares)				9,700,000
Ownership interest before initial public offering (as a percent)					24.00%
Ownership interest after initial public offering (as a percent)					20.00%
Decrease in carrying value of Symetra from dilution				$ 16.0
Ownership interest (as a percent)	15.00%
Fair value of investment	261.0
Estimated fair value of investment per share	$ 15	$ 16	$ 30
Number of valuation techniques	3
Number of representatives	2
After-tax equity in losses of unconsolidated affiliates	45.9
Equity in net unrealized gains (losses)	$ 136.6
Risk free interest rate (as a percent)	0.31%
Volatility rate (as a percent)	36.00%
Expected life (in years)	2.58
Strike price (in dollars per share)	$ 11.49
Share price (in dollars per share)	$ 9.07