Note 2 - Details of Consolidated Balance Sheet Accounts (Details) - Prepaid Expenses and Other (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Note 2 - Details of Consolidated Balance Sheet Accounts (Details) - Prepaid Expenses and Other [Line Items]
Insurance premiums	$ 1,537us-gaap_PrepaidInsurance	$ 1,384us-gaap_PrepaidInsurance
Other	2,734us-gaap_OtherAssetsCurrent	2,606us-gaap_OtherAssetsCurrent
	16,860	15,274
Tires in Service [Member]
Note 2 - Details of Consolidated Balance Sheet Accounts (Details) - Prepaid Expenses and Other [Line Items]
Prepaid expenses	4,438	3,982
License Fees [Member]
Note 2 - Details of Consolidated Balance Sheet Accounts (Details) - Prepaid Expenses and Other [Line Items]
Prepaid expenses	4,397	4,169
Parts and Tires in Inventory [Member]
Note 2 - Details of Consolidated Balance Sheet Accounts (Details) - Prepaid Expenses and Other [Line Items]
Prepaid expenses	$ 3,754	$ 3,133

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Aggregate carrying amount, as of the balance sheet date, of current assets not separately disclosed in the balance sheet. Current assets are expected to be realized or consumed within one year (or the normal operating cycle, if longer).

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