| **Quarterly Financial Data (Schedule Of Quarterly Financial Data) (Details) (USD $)In Thousands, except Per Share data, unless otherwise specified** | 3 Months Ended | 12 Months Ended |
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| **Quarterly Financial Data [Abstract]**                                                                                                              |           |            |   |   |   |   |   |   |   |   |   |
| Revenue, Net                                                                                                                                         | $ 594,789      | $ 608,819       | $ 573,470 | $ 529,654 | $ 538,130 | $ 559,183 | $ 568,145 | $ 565,774 | $ 2,306,732 | $ 2,231,232 | $ 2,013,393 |
| Gross Profit                                                                                                                                         | 56,244         | 57,393          | 54,624 | 51,652 | 50,288 | 54,074 | 55,470 | 54,910 | 219,913 | 214,742 | 206,922 |
| Net income                                                                                                                                           | $ 728          | $ 23,533        | $ 19,958 | $ 17,870 | $ 18,323 | $ 22,040 | $ 23,860 | $ 25,033 | $ 62,089 | $ 89,256 | $ 89,533 |
| Earnings Per Share, Basic                                                                                                                            | $ 0.02         | $ 0.67          | $ 0.57 | $ 0.52 | $ 0.53 | $ 0.60 | $ 0.60 | $ 0.62 | $ 1.78 | $ 2.34 | $ 2.24 |
| Earnings Per Share, Diluted                                                                                                                          | $ 0.02         | $ 0.66          | $ 0.56 | $ 0.51 | $ 0.52 | $ 0.58 | $ 0.59 | $ 0.61 | $ 1.75 | $ 2.30 | $ 2.19 |

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| - Definition
The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.
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| - Definition
The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.
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| - Definition
Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.
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| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
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| - Definition
Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.
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