Debt Level 4 (Details) (USD $) In Thousands | Sep. 30, 2011 | Dec. 31, 2010 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Bank credit facility due March 2016 | $ 65,000 | $ 0 |
| Total debt | 1,887,584 | 1,854,882 |
| Less current maturities | (23,685) | (22,502) |
| Total long-term debt | 1,863,899 | 1,832,380 |
Unsecured Debt [Member] | ||
| Debt Instrument [Line Items] | ||
| Unamortized pricing discounts and other | (5,030) | (6,106) |
Unsecured Debt [Member] | February 2013 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 4,857 | 8,557 |
Unsecured Debt [Member] | October 2014 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 180,692 | 180,692 |
Unsecured Debt [Member] | April 2015 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 136,465 | 157,250 |
Unsecured Debt [Member] | April 2016 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 197,377 | 212,927 |
Unsecured Debt [Member] | June 2017 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 295,000 | 295,000 |
Unsecured Debt [Member] | October 2018 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 250,000 | 250,000 |
Unsecured Debt [Member] | May 2019 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 250,000 | 250,000 |
Unsecured Debt [Member] | November 2021 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 150,000 | 150,000 |
Unsecured Debt [Member] | April 2027 [Member] | ||
| Debt Instrument [Line Items] | ||
| Senior Notes | 200,000 | 200,000 |
Capital Lease Obligations [Member] | ||
| Debt Instrument [Line Items] | ||
| Obligations under capital leases | 126,658 | 118,339 |
Mortgages [Member] | ||
| Debt Instrument [Line Items] | ||
| Mortgage notes and other debt, maturities through 2047 | $ 36,565 | $ 38,223 |