Investments in Unconsolidated Affiliates (Symetra) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				12 Months Ended		3 Months Ended			3 Months Ended		6 Months Ended			12 Months Ended			12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Symetra	Mar. 31, 2013 Symetra	Dec. 31, 2011 Symetra	Jun. 20, 2013 Symetra	Mar. 31, 2014 Common Stock Symetra	Mar. 31, 2013 Common Stock Symetra	Dec. 31, 2011 Common Stock Symetra	Mar. 31, 2014 Warrants Symetra	Mar. 31, 2013 Warrants Symetra	Jun. 20, 2013 Symetra Common Stock	Mar. 31, 2014 equity in earnings of unconsolidated affiliates [Member] Symetra	Jun. 20, 2013 equity in earnings of unconsolidated affiliates [Member] Symetra	Dec. 31, 2011 equity in earnings of unconsolidated affiliates [Member] Common Stock Symetra	Mar. 31, 2014 Net unrealized gains (losses) of unconsolidated affiliates [Member] Symetra	Jun. 20, 2013 Net unrealized gains (losses) of unconsolidated affiliates [Member] Symetra	Dec. 31, 2011 Net unrealized gains (losses) of unconsolidated affiliates [Member] Common Stock Symetra
Investments in unconsolidated affiliates
Shares of Symetra Financial Corporation owned (in shares)			20,050,000
Ownership interest (as a percent)			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	$ 586.00	$ 564.00										$ 13.44
Unamortized basis difference						$ 19.3								$ 0.4			$ 18.9
Fair value of investment									261.0
Estimated fair value of investment per share									$ 15
Other than Temporary Impairment Losses, Investments															45.9			136.6
Term of amortization (in years)					30 years
Weight Average Years Remaining			29 years
After tax amortization through equity in earnings			0.7
After tax amortization through equity in net unrealized losses			2.9
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity			183.3
Pre-tax unamortized basis difference													39.0			144.3
Expected life (in years)											1 year 1 month 90 days
Class of warrant or right fair value assumptions per strike price											11.49
Proceeds from Equity Method Investment, Dividends or Distributions			2.0	1.4			2.0	1.4		0	0
Proceeds from Dividends Received											$ 0.8
Fair Value Assumptions, Risk Free Interest Rate											0.17%
Fair Value Assumptions, Expected Volatility Rate											29.10%
Share Price							$ 19.82				$ 13.41