Note 9 - Notes Payable (Detail)	1 Months Ended	3 Months Ended	1 Months Ended
	Jan. 31, 2013 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2013 Medium-term Notes [Member] MXN	Mar. 31, 2008 Medium-term Notes [Member] MXN	Mar. 31, 2013 Medium-term Notes [Member] USD ($)	Jan. 31, 2013 Medium-term Notes [Member]
Proceeds from Issuance of Unsecured Debt (in Pesos)		$ 78,118,000	1,000,000,000	1,000,000,000
Debt Instrument, Interest Rate, Stated Percentage				8.58%		6.125%
Debt Instrument, Term					5 years
Debt Instrument, Basis Spread on Variable Rate					1.35%
Debt Instrument, Interest Rate, Effective Percentage					6.13%
Long-term Debt (in Pesos)			1,000,000,000		80,900,000
Long-term Debt (in Dollars)			1,000,000,000		80,900,000
Repayments of Medium-term Notes (in Dollars)	$ 100,000,000