Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financial assets and liabilities recorded at fair value on a recurring basis
Available-for-sale securities, fair value disclosure	$ 31,582	$ 31,570
Trading securities, fair value disclosure	30,486	35,092
Fair Value, Measurements, Recurring [Member]
Financial assets and liabilities recorded at fair value on a recurring basis
Available-for-sale securities, fair value disclosure	31,582	31,570
Trading securities, fair value disclosure	30,486	35,092
Total assets	62,068	66,662
Fair value of interest rate swap agreements	254,228	340,526
Total liabilities	254,228	340,526
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Financial assets and liabilities recorded at fair value on a recurring basis
Available-for-sale securities, fair value disclosure	31,582	31,570
Trading securities, fair value disclosure	30,486	35,092
Total assets	62,068	66,662
Fair value of interest rate swap agreements	0	0
Total liabilities	0	0
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Financial assets and liabilities recorded at fair value on a recurring basis
Available-for-sale securities, fair value disclosure	0	0
Trading securities, fair value disclosure	0	0
Total assets	0	0
Fair value of interest rate swap agreements	254,228	340,526
Total liabilities	254,228	340,526
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Financial assets and liabilities recorded at fair value on a recurring basis
Available-for-sale securities, fair value disclosure	0	0
Trading securities, fair value disclosure	0	0
Total assets	0	0
Fair value of interest rate swap agreements	0	0
Total liabilities	$ 0	$ 0

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Trading Securities which consist of all investments in certain debt and equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for which an entity has elected the fair value option. Trading generally reflects active and frequent buying and selling, and trading securities are generally used with the objective of generating profits on short-term differences in price, but this category of investments may also include items which are not intended to be sold in the near term or for which the fair value option has been elected.

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