Note 7 - Fair Value Measurements - Level 3 Fair Value Measurements (Details) - Valuation, Market Approach [Member]	Mar. 31, 2018	Dec. 31, 2017
Measurement Input, Discount Rate [Member] | Minimum [Member]
Discount rate	5.5	5.5
Measurement Input, Discount Rate [Member] | Maximum [Member]
Discount rate	13.25	13.25
Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Discount rate	5.92	5.92
Measurement Input, Cost to Sell [Member] | Minimum [Member]
Level 3 Fair Value Measurements	5	2
Measurement Input, Cost to Sell [Member] | Maximum [Member]
Level 3 Fair Value Measurements	6.01	6.01
Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Level 3 Fair Value Measurements	5.14	4.72
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Minimum [Member]
Level 3 Fair Value Measurements	1.68	1.68
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Maximum [Member]
Level 3 Fair Value Measurements	86.03	68.33
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Weighted Average [Member]
Level 3 Fair Value Measurements	13.35	11.07