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Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended
--- | ---
Jun. 30, 2016 | Mar. 31, 2016 | Mar. 31, 2015
Subsequent Event [Line Items] |  |  |
Other Underwriting Expense |  | $ 55.4 | $ 56.0
Payments to Acquire Other Investments |  | 10.9 | $ 6.5
Subsequent Event [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Proceeds from Divestiture of Interest in Subsidiaries and Affiliates | $ 2,600.0 |  |
Payments to Acquire Other Investments | (161.8) |  |
Stock Repurchased and Retired During Period, Value | $ 287.0 |  |
Treasury Stock Acquired, Average Cost Per Share | $ 807 |  |
UNITED STATES |  |  |
Subsequent Event [Line Items] |  |  |
Stop Loss Limitation |  | 45.0 |
Industry Loss Trigger on Industry Loss Warranty |  | 15,000.0 |
UNITED STATES | Combination One [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Stop Loss Limitation |  | 75.0 |
Industry Loss Trigger on Industry Loss Warranty |  | 40,000.0 |
UNITED STATES | Combination Two [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Stop Loss Limitation |  | 22.5 |
Industry Loss Trigger on Industry Loss Warranty |  | 50,000.0 |
JAPAN |  |  |
Subsequent Event [Line Items] |  |  |
Stop Loss Limitation |  | 25.0 |
Industry Loss Trigger on Industry Loss Warranty |  | $ 12,500.0 |
Common Stock [Member] | Subsequent Event [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Stock Repurchased and Retired During Period, Shares | 356,423 |  |
Franklin Mutual Advisers [Member] | Subsequent Event [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Stock Repurchased and Retired During Period, Shares | 325,000 |  |
Treasury Stock Acquired, Average Cost Per Share | $ 807 |  |

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- Definition Costs incurred during the period, such as those relating to general administration and policy maintenance that do not vary with and are not primarily related to the acquisition or renewal of insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 720 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35755714&loc=d3e28434-158551 + Details
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