Debt Debt (Schedule of Long-Term Debt) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	$ 329,761	$ 357,576
Less current installments on long-term debt	9,013	8,413
Long-term debt	320,748	349,163
Revenue Bond, fixed rate 5.9% to 7.75%, due 2013 through 2026 [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	116,993	144,627
Repayments of Other Long-term Debt	27,650
7.5% Senior Notes, due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	148,305	148,241
Debentures, 6.95%, due 2015 [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	22,494	22,493
Medium-term Notes, fixed rate 8.75% to 8.89%, due 2016 through 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	27,250	27,250
Term Loans [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	12,000	12,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	2,706	2,952
Other notes [Member]
Debt Instrument [Line Items]
Long-term debt, including current installments on long-term debt	$ 13	$ 13
Minimum [Member] \| Revenue Bond, fixed rate 5.9% to 7.75%, due 2013 through 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.25%
Maximum [Member] \| Revenue Bond, fixed rate 5.9% to 7.75%, due 2013 through 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.75%

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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-Publisher SEC

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Interest rate stated in the contractual debt agreement.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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+ References

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The cash outflow attributable to repayments of borrowings not otherwise defined in the taxonomy (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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