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Retirement Plans (Retirement Savings Plan) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Minimum Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 2.00% |  |
Maximum Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 50.00% |  |
Retirement Savings Plan [Member] |  |  |
Employer contribution | $ 8.2 | $ 7.0 | $ 6.3
Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  |  | 7.00%
Vesting Period Of Employer Contribution |  | 6 years |
Defined Contribution Plan, Employer Matching Contribution, Percent |  |  | 65.00%
Enhanced Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  |  | 2.00%
Defined Contribution Plan, Employer Matching Contribution, Percent |  |  | 100.00%
Non Elective Employer Contribution [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  | 4.00% | 2.00%
Vesting Period Of Employer Contribution |  | 3 years |
First Tier Of Employee Contributions [Member] | Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution To Retirement Savings Plan Percentage |  | 100.00% |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  | 3.00% |
Second Tier Of Employee Contributions [Member] | Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  | 3.00% |
Defined Contribution Plan, Employer Matching Contribution, Percent |  | 50.00% |

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- Definition Maximum percentage of defined compensation that an employee can contribute to the Retirement Savings Plan. + References No definition available. + Details
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- Definition Maximum percentage of an employee's contribution to the Retirement Savings Plan that the employer will match. + References No definition available. + Details
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- Definition Percentage of an employee's contribution to the Retirement Savings Plan that the employer will match. + References No definition available. + Details
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- Definition Minimum percentage of defined compensation that an employee can contribute to the Retirement Savings Plan. + References No definition available. + Details
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- Definition The period of time over which an employee is required to provide service in exchange for the employer match of the Retirement Savings Plan. + References No definition available. + Details
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Balance Type: | na
Period Type: | instant

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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph b -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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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