Fair Value Of Assets And Liabilities (Recurring Fair Value Measurements) (Details) (USD $)
In Thousands | Sep. 30, 2011 | Dec. 31, 2010 |
|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
| Restricted funds | $ 66,593 | $ 120,784 |
| Rabbi trust investments | 779 | 1,552 |
| Deposits | 1,646 | 1,381 |
| Mark-to-market derivative asset | 5,612 | 0 |
| Total assets | 74,630 | 123,717 |
| Deferred compensation obligation | 8,868 | 9,180 |
| Mark-to-market derivative liability | 0 | 898 |
| Total liabilities | 8,868 | 10,078 |
| Total net assets (liabilities) | 65,762 | 113,639 |
Level 1 [Member] | | |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
| Restricted funds | 66,593 | 120,784 |
| Rabbi trust investments | | |
| Deposits | 1,646 | 1,381 |
| Mark-to-market derivative asset | | |
| Total assets | 68,239 | 122,165 |
| Deferred compensation obligation | | |
| Mark-to-market derivative liability | | |
| Total liabilities | | |
| Total net assets (liabilities) | 68,239 | 122,165 |
Level 2 [Member] | | |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
| Rabbi trust investments | 779 | 1,552 |
| Mark-to-market derivative asset | 5,612 | 0 |
| Total assets | 6,391 | 1,552 |
| Deferred compensation obligation | 8,868 | 9,180 |
| Mark-to-market derivative liability | 0 | 898 |
| Total liabilities | 8,868 | 10,078 |
| Total net assets (liabilities) | (2,477) | (8,526) |
Level 3 [Member] | | |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
| Restricted funds | | |
| Rabbi trust investments | | |
| Deposits | | |
| Mark-to-market derivative asset | | |
| Total assets | | |
| Deferred compensation obligation | | |
| Mark-to-market derivative liability | | |
| Total liabilities | | |
| Total net assets (liabilities) | | |