Note 3 - Variable Interest Entities (Details) - Carrying Amounts and Classification of Assets and Liabilities of Shield Stations (Parentheticals) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Trade accounts receivable, allowance for doubtful accounts	$ 2,694	$ 2,772
Shield Stations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Trade accounts receivable, allowance for doubtful accounts	$ 119	$ 105