Note 12 - Notes Payable (Details) - Notes Payable - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Balance (in Dollars)	[1]	$ 3,761,328		$ 3,171,742
Interest Rate Range (Low)		3.62%
Interest Rate Range (High)		4.97%
Balance (in Dollars)	[2]	$ (31,400)		(20,500)
Senior Note 1 [Member]
Debt Instrument [Line Items]
Balance (in Dollars)		$ 2,290,900		$ 1,540,900
Interest Rate Range (Low)		3.13%		3.13%
Interest Rate Range (High)		6.88%		6.88%
Medium-term Notes [Member]
Debt Instrument [Line Items]
Balance (in Dollars)		$ 600,000		$ 850,000
Interest Rate Range (Low)		4.30%		4.30%
Interest Rate Range (High)		5.78%		5.78%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Balance (in Dollars)		$ 650,000	[3]	$ 400,000	[4]
Interest Rate Range (Low)					[4]
Interest Rate Range (High)					[4]
Canadian Notes Payable [Member]
Debt Instrument [Line Items]
Balance (in Dollars)		$ 251,800		$ 301,300
Interest Rate Range (Low)		3.86%		3.86%
Interest Rate Range (High)		5.99%		5.99%
Line of Credit [Member]
Debt Instrument [Line Items]
Balance (in Dollars)	[5]			$ 100,000
Interest Rate Range (Low)
Interest Rate Range (High)

[1] The Company determined that its valuation of these Notes Payable was classified within Level 2 of the fair value hierarchy.

[2] In April 2015, the FASB issued ASU 2015-03, which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Beginning in its fiscal year 2015, the Company elected to early adopt ASU 2015-03 and retrospectively applied the guidance to its Notes Payable to all periods presented.

[3] Interest rate is equal to LIBOR + 0.95% (1.37% at December 31, 2015).

[4] Interest rate is equal to LIBOR + 1.05% (1.21% at December 31, 2014).

[5] Interest rate is equal to LIBOR + 0.925% (1.35% and 1.09% at December 31, 2015 and 2014, respectively).