Investments - Schedule of Investments (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended | 12 Months Ended |
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Sep. 30, 2011 | Dec. 31, 2010 |
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| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Debt Securities | $ 4,782.4 | $ 4,475.3 |
| Available-for-sale Securities, Equity Securities | 360.8 | 550.4 |
| Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] | | |
| Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value | 466.7 | |
| Available-for-sale Securities, Debt Maturities, within One Year, Fair Value | 90.3 | |
| Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value | 942.2 | |
| Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value | 2,978.3 | |
| Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value | 304.9 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 355.5 | 617.9 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (21.1) | (21.5) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 90.8 | 122.2 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (7.4) | (12.7) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 446.3 | 740.1 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (28.5) | (34.2) |
| Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Related to Securities that have Previously Recognized Foregin Currency Impairment | 0.1 | (0.1) |
| Number of Issuers of Available for Sales Securities Continuous Unrealized Loss Possition Aggregate Losses Related to Securities that have Previously Recognized Foreign Currency impairment | 1 | 1 |
| Percentage of Unrealized Loss Postion to Amortized Cost Basis of Available for Sale Security Average | | 4.00% |
| Accrued Expenses and Other Liabilities | 390.7 | 437.8 |
External Credit Rating, Investment Grade [Member] | Debt Securities [Member] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | 4.8 | (28.1) |
External Credit Rating, Non Investment Grade [Member] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Related to Securities that have Previously Recognized Foregin Currency Impairment | 0.1 | (0.1) |
| Percentage of Unrealized Loss Postion to Amortized Cost Basis of Available for Sale Security Average | 5.00% | |
External Credit Rating, Non Investment Grade [Member] | Debt Securities [Member] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | 7.3 | (4.1) |
Equity Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 22.2 | 103.2 |
| Available-for-sale Securities, Gross Unrealized Losses | (16.4) | (2.0) |
| Available-for-sale Securities, Equity Securities | 360.8 | 550.4 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 355.0 | 449.2 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 176.3 | 20.1 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (15.3) | (0.8) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 6.5 | 13.2 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (1.1) | (1.2) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 182.8 | 33.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (16.4) | (2.0) |
Preferred Stock Finance Insurance and Real Estate [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 0.8 | 3.5 |
| Available-for-sale Securities, Gross Unrealized Losses | (6.3) | (0.2) |
| Available-for-sale Securities, Equity Securities | 88.9 | 97.7 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 94.4 | 94.4 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 52.4 | 3.0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (5.6) | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 2.1 | 2.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (0.7) | (0.2) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 54.5 | 5.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (6.3) | (0.2) |
Preferred Stocks Other Industries [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 2.6 | 7.6 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.7) | (0.2) |
| Available-for-sale Securities, Equity Securities | 20.2 | 27.4 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 18.3 | 20.0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 3.2 | 0.7 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (0.6) | (0.1) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 2.8 | 2.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (0.1) | (0.1) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 6.0 | 3.5 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.7) | (0.2) |
Common Stock Intermec [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | | 50.6 |
| Available-for-sale Securities, Gross Unrealized Losses | | 0 |
| Available-for-sale Securities, Equity Securities | | 137.5 |
| Available-for-sale Equity Securities, Amortized Cost Basis | | 86.9 |
Common Stocks Manufacturing [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 9.6 | 14.6 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.9) | (0.3) |
| Available-for-sale Securities, Equity Securities | 72.3 | 89.6 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 63.6 | 75.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 11.2 | 7.9 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (0.9) | (0.3) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 1.7 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 11.2 | 9.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.9) | (0.3) |
Common Stocks Other Industries [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 4.0 | 6.6 |
| Available-for-sale Securities, Gross Unrealized Losses | (2.8) | (0.1) |
| Available-for-sale Securities, Equity Securities | 41.5 | 43.8 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 40.3 | 37.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 15.7 | 6.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (2.8) | (0.1) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 15.7 | 6.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (2.8) | (0.1) |
Exchange Traded Funds [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 0.1 | 2.7 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.4) | 0 |
| Available-for-sale Securities, Equity Securities | 65.7 | 79.2 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 66.0 | 76.5 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 50.5 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (0.4) | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | 0 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 50.5 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.4) | |
Partnership Interest [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 5.1 | 17.6 |
| Available-for-sale Securities, Gross Unrealized Losses | (5.3) | (1.2) |
| Available-for-sale Securities, Equity Securities | 72.2 | 75.2 |
| Available-for-sale Equity Securities, Amortized Cost Basis | 72.4 | 58.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 43.3 | 2.2 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (5.0) | (0.3) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1.6 | 6.1 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (0.3) | (0.9) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 44.9 | 8.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (5.3) | (1.2) |
Debt Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 507.4 | 266.7 |
| Available-for-sale Securities, Gross Unrealized Losses | (12.1) | (32.2) |
| Available-for-sale Securities, Debt Securities | 4,782.4 | 4,475.3 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 4,287.1 | 4,240.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 179.2 | 597.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (5.8) | (20.7) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 84.3 | 109.0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (6.3) | (11.5) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 263.5 | 706.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (12.1) | (32.2) |
| Accrued Expenses and Other Liabilities | 4.9 | 0 |
US Government and Government Agencies and Authorities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 52.0 | 28.4 |
| Available-for-sale Securities, Gross Unrealized Losses | 0 | (0.1) |
| Available-for-sale Securities, Debt Securities | 516.7 | 536.9 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 464.7 | 508.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 1.3 | 18.5 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | 0 | (0.1) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0.1 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 1.3 | 18.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | 0 | (0.1) |
Government National Mortgage Association Certificates and Obligations (GNMA) [Member] | | |
| Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] | | |
| Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value | 268.2 | |
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | | |
| Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] | | |
| Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value | 30.1 | |
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | | |
| Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] | | |
| Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value | 0.9 | |
Other Issuers [Member] | | |
| Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] | | |
| Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value | 5.7 | |
US States and Political Subdivisions Debt Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 143.1 | 53.5 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.8) | (20.7) |
| Available-for-sale Securities, Debt Securities | 1,903.3 | 1,792.8 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 1,761.0 | 1,760.0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 0 | 455.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | 0 | (16.9) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 12.3 | 16.5 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (0.8) | (3.8) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 12.3 | 472.1 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.8) | (20.7) |
Corporate Debt Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 307.8 | 178.8 |
| Available-for-sale Securities, Gross Unrealized Losses | (10.3) | (10.1) |
| Available-for-sale Securities, Debt Securities | 2,275.2 | 2,049.0 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 1,977.7 | 1,880.3 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 176.9 | 123.0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (5.5) | (3.7) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 67.4 | 87.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (4.8) | (6.4) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 244.3 | 210.8 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (10.3) | (10.1) |
Redeemable Preferred Stock [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 3.4 | 4.9 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.3) | 0 |
| Available-for-sale Securities, Debt Securities | 81.5 | 88.3 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 78.4 | 83.4 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 1.0 | 0.7 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | (0.3) | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1.7 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 2.7 | 0.7 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.3) | 0 |
Asset-backed Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Gross Unrealized Gains | 1.1 | 1.1 |
| Available-for-sale Securities, Gross Unrealized Losses | (0.7) | (1.3) |
| Available-for-sale Securities, Debt Securities | 5.7 | 8.3 |
| Available-for-sale Debt Securities, Amortized Cost Basis | 5.3 | 8.5 |
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] | | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses | 0 | 0 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 2.9 | 4.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses | (0.7) | (1.3) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 2.9 | 4.6 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses | (0.7) | (1.3) |
Mortgage-backed Securities, Issued by Private Enterprises [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Debt Securities | 1.8 | 1.9 |
Other Asset Backed Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Debt Securities | 0.6 | 1.2 |
Collateralized Debt Obligations [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Debt Securities | 3.2 | 5.0 |
Commercial Mortgage Backed Securities [Member] | | |
| Schedule of Available-for-sale Securities [Line Items] | | |
| Available-for-sale Securities, Debt Securities | $ 0.1 | $ 0.2 |