Note 12 - Notes Payable (Details)	12 Months Ended				1 Months Ended			12 Months Ended		1 Months Ended				12 Months Ended		12 Months Ended	1 Months Ended		12 Months Ended	1 Months Ended									12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Apr. 30, 2007 USD ($)	Jan. 31, 2015 Subsequent Event [Member] Term Loan [Member] London Interbank Offered Rate (LIBOR) [Member]	Jan. 31, 2015 Subsequent Event [Member] Term Loan [Member] USD ($)	Jul. 31, 2013 Canada, Dollars Unsecured Debt [Member] CAD	Dec. 31, 2014 Term Loan [Member] London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2013 Term Loan [Member] London Interbank Offered Rate (LIBOR) [Member]	Sep. 30, 2014 Term Loan [Member] USD ($)	Sep. 30, 2014 Term Loan [Member] MXN	Dec. 31, 2014 Term Loan [Member]	Dec. 31, 2013 Term Loan [Member]	Dec. 31, 2014 Line of Credit [Member] London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2014 Line of Credit [Member]	Dec. 31, 2013 Mexican Term Loan [Member] TIIE [Member]	Mar. 31, 2013 Mexican Term Loan [Member] MXN	Dec. 31, 2013 Mexican Term Loan [Member]	Dec. 31, 2014 Unsecured Debt [Member] London Interbank Offered Rate (LIBOR) [Member]	Apr. 30, 2014 Unsecured Debt [Member] USD ($)	May 31, 2013 Unsecured Debt [Member] USD ($)	Apr. 30, 2007 Unsecured Debt [Member] USD ($)	Dec. 31, 2014 Unsecured Debt [Member] USD ($)	Jul. 31, 2013 Series 4 Unsecured Debt [Member] CAD	Mar. 31, 2014 Revolving Credit Facility [Member] USD ($)	Mar. 31, 2014 Previous Credit Facility [Member] USD ($)	Mar. 31, 2014 Including Accordion Feature [Member] USD ($)	Dec. 31, 2014 Letter of Credit [Member] USD ($)	Dec. 31, 2014 London Interbank Offered Rate (LIBOR) [Member]
Note 12 - Notes Payable (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate					0.95%			1.05%	1.05%					0.925%		1.35%			1.05%										0.925%
Debt Instrument, Interest Rate, Effective Percentage												1.21%	1.22%		1.09%			5.15%
Repayments of Long-term Debt						$ 400,000,000				$ 76,300,000	1,000,000,000
Unsecured Debt						650,000,000																	400,000,000
Debt, Weighted Average Interest Rate																							4.17%
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months																							750,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Two																							300,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Three																							290,900,000
Long-term Debt, Maturities, Repayments of Principal in Year Four																							529,100,000
Long-term Debt, Maturities, Repayments of Principal in Year Five																							300,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																							1,022,200,000
Proceeds from Issuance of Senior Long-term Debt																				495,400,000	344,700,000	300,000,000
Debt Covenants, Dividend Payment Restriction, Maximum Payment				26,000,000
Debt Instrument, Face Amount																				500,000,000	350,000,000			200,000,000
Debt Instrument, Term																	5 years			7 years	10 years
Debt Instrument, Interest Rate, Stated Percentage							5.18%										8.58%			3.20%	3.125%			3.855%
Debt Issuance Cost																					500,000
Repayments of Senior Debt																					75,000,000
Repayments of Medium-term Notes (in Dollars)							200,000,000
Line of Credit Facility, Maximum Borrowing Capacity																									1,750,000,000	1,750,000,000	2,250,000,000
Line of Credit Facility, Sub Limit	500,000,000
Long-term Line of Credit	100,000,000																											1,000,000
Number of Additional One-Year Options																							3
Proceeds from Issuance of Medium-term Notes (in Pesos)																	1,000,000,000
Repayments of Unsecured Debt (in Pesos)	$ 370,842,000	$ 546,717,000	$ 215,900,000														1,000,000,000