| **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, 2013 are as follows (in millions): Cash & Cash Equivalents Restricted Cash Restricted Marketable Securities TotalCash$64.5 $52.4 $— $116.9Equity securities— — 47.6 47.6Total$64.5 $52.4 $47.6 $164.5The components of our investments as of December 31, 2014 are as follows (in millions): Cash & Cash Equivalents Restricted Cash Restricted Marketable Securities TotalCash$66.7 $45.6 $— $112.3Equity securities— — 50.5 50.5Total$66.7 $45.6$50.5 $162.8 |
| Schedule of Restricted Cash                                        | As of December 31, 2014 and 2013, Restricted cash consisted of the following (in millions): As of December 31, 2014 2013Affiliate cash$13.1 $13.6Self-insured captive funds32.4 37.8Paid-loss deposit funds0.1 1.0Total restricted cash$45.6 $52.4                                                                                                                                                                                                                                                                                                                                                                                                             |
| Available-for-sale Securities Cost to Fair Value Reconciliation    | A summary of our restricted marketable securities as of December 31, 2014 is as follows (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Fair ValueEquity securities$51.3 $0.5 $(1.3) $50.5A summary of our restricted marketable securities as of December 31, 2013 is as follows (in millions): Cost Gross Unrealized Gains Gross Unrealized Losses Fair ValueEquity securities$47.9 $0.2 $(0.5) $47.6                                                                                                                                                                                             |
| Investment information related to restricted marketable securities | Investing information related to our restricted marketable securities is as follows (in millions): For the Year Ended December 31, 2014 2013 2012Proceeds from sales of restricted available-for-sale securities$— $16.6 $—Proceeds from sales of nonrestricted available-for-sale securities$2.7 $— $—Gross realized gains$0.5 $1.0 $—Gross realized losses$(0.1) $(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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563
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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.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5Reference 3: 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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