Long-Term Debt (Schedule Of Outstanding Debt) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Debt Issuance [Line Items]
Senior revolving credit facility maturing in 2016	$ 170,000	$ 195,000
Note payable through 2011, net of unamortized discount of $66		1,934
Total	342,046	377,094
Amounts due within one year	8,000	10,000
Long-term debt	334,046	367,094
Debt instrument, unamortized discount	66
Industrial Development Debt Issues Payable Through 2022, 0.30% [Member]
Debt Issuance [Line Items]
Industrial development debt issues payable through 2022, 0.30%	4,000	4,000
Debt instruments maturity date	2022
Senior Notes, interest rate	0.30%
Senior Notes Payable Through 2012, 8.39% [Member]
Debt Issuance [Line Items]
Senior Notes	8,046	16,160
Debt instruments maturity date	2012
Senior Notes, interest rate	8.39%
Senior Notes Payable Through 2021, 5.41% [Member]
Debt Issuance [Line Items]
Senior Notes	60,000	60,000
Debt instruments maturity date	2021
Senior Notes, interest rate	5.41%
Senior Notes Payable Through 2021, 4.00% [Member]
Debt Issuance [Line Items]
Senior Notes	$ 100,000	$ 100,000
Debt instruments maturity date	2021
Senior Notes, interest rate	4.00%

Debt instruments maturity date.

No definition available.

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- Definition

Industrial development debt issues payable.

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- Definition

Interest rate stated in the contractual debt agreement.

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- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. 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, and after deducting unamortized discount or premiums, if any.

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Total of the portions of the carrying amounts as of the balance sheet date of long-term debt, which may include notes payable, bonds payable, debentures, mortgage loans, and commercial paper, which are scheduled to be repaid within one year or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

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