Note 17 - Preferred Stock, Common Stock and Convertible Unit Transactions (Details Textual) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 shares
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares		$ 0.01	$ 0.01
Stock Repurchased During Period, Shares (in shares) | shares		294,346	223,609	278,566
Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance		$ 62,210	$ 64,015
Partners' Capital Account, Units, Converted (in shares) | shares		700,000
Share Repurchase Program [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares		$ 0.01
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 224,900
Stock Repurchase Program, Authorized Amount		$ 300,000
Stock Repurchased During Period, Shares (in shares) | shares		0	0
ATM Program [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares	$ 0.01
Maximum Aggregate Sales Price	$ 500,000
Stock Issued During Period, Shares, New Issues (in shares) | shares		0	9,514,544
Proceeds from Issuance of Common Stock			$ 200,100
Payments of Stock Issuance Costs			$ 1,800
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 298,100
Series I, J, K, L or M Preferred Stock [Member]
Number of Votes		1,000
Number of Proxies		1,000
Number of Votes, Depositary		1
Series I Preferred Stock [Member]
Preferred Stock, Liquidation Preference Per Share (in dollars per share) | $ / shares		$ 25,000
Series J Preferred Stock [Member]
Preferred Stock, Liquidation Preference Per Share (in dollars per share) | $ / shares		25,000
Depositary Share [Member]
Preferred Stock, Liquidation Preference Per Share (in dollars per share) | $ / shares		$ 25.00
Convertible Units [Member]
Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance		$ 10,900