Fair Value (Fair Value Of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 628.3	$ 820.4	$ 218.8	$ 290.4
Fixed maturities	6,470.6	6,284.7
Equity securities	334.1	246.4
Mortgage loans	4.8
Other investments	212.8	190.2
Debt	918.1	911.1
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	628.3	820.4
Fixed maturities	6,470.6	6,284.7
Equity securities	334.1	246.4
Mortgage loans	4.5	4.7
Other investments	149.6	135.1
Total financial assets	7,587.1	7,491.3
Debt	918.1	911.1
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	628.3	820.4
Fixed maturities	6,470.6	6,284.7
Equity securities	334.1	246.4
Mortgage loans	4.8	5.0
Other investments	149.4	135.1
Total financial assets	7,587.2	7,491.6
Debt	$ 997.6	$ 1,014.9

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).

+ References

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+ Details

- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

+ References+ Details