| **Cash and Marketable Securities (Tables)**                        | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                       |
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| **Cash and Cash Equivalents [Abstract]**                           |                                                                                                                                                                                                                                                                                                                                                                                  |   |
| Schedule of Investment Components                                  | The components of our investments as of December 31, 2012 are as follows (in millions):  Cash & Cash Equivalents Restricted Cash Restricted Marketable Securities TotalCash$132.8 $49.3 $— $182.1Equity securities— — 55.8 55.8Total$132.8 $49.3$55.8 $237.9                              | The components of our investments as of December 31, 2011 are as follows (in millions):  Cash & Cash Equivalents Restricted Cash Restricted Marketable Securities TotalCash$30.1 $35.3 $— $65.4Equity securities— — 45.2 45.2Total$30.1 $35.3 $45.2 $110.6 |
| Schedule of Restricted Cash                                        | As of December 31, 2012 and 2011, Restricted cash consisted of the following (in millions):  As of December 31, 2012 2011Affiliate cash$22.5 $11.1Self-insured captive funds26.0 23.5Paid-loss deposit funds0.8 0.7Total restricted cash$49.3 $35.3                                                                                      |   |
| Available-for-sale Securities Cost to Fair Value Reconciliation    | A summary of our restricted marketable securities as of December 31, 2012 is as follows (in millions):  Cost Gross Unrealized Gains Gross Unrealized Losses Fair ValueEquity securities$54.4 $1.5 $(0.1) $55.8                                                                                                                           | A summary of our restricted marketable securities as of December 31, 2011 is as follows (in millions):  Cost Gross Unrealized Gains Gross Unrealized Losses Fair ValueEquity securities$45.2 $0.7 $(0.7) $45.2 |
| Investment information related to restricted marketable securities | Investing information related to our restricted marketable securities is as follows (in millions):  For the Year Ended December 31, 2012 2011 2010Proceeds from sales of restricted available-for-sale securities$— $— $5.2Gross realized gains$— $— $0.4Gross realized losses$— $— $(0.1) |   |

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| - Definition
Tabular disclosure of the Company's investments by type.
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| - Definition
Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value.
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No definition available.
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| - Definition
Tabular disclosure of the proceeds from sales of available-for-sale securities and the gross realized gains and gross realized losses that have been included in earnings as a result of those sales.
+ References
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| - Definition
Tabular disclosure of the cash and cash items which are restricted as to withdrawal or usage. The provisions of any restrictions are described in a note to the financial statements. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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