Note 6 - Long-term Debt and Lease Obligation (Details Textual)				1 Months Ended	12 Months Ended
	May 25, 2017 USD ($) $ / shares shares	Apr. 26, 2016 USD ($)	Feb. 08, 2016 USD ($) a	May 31, 2017 USD ($)	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares
Convertible Debt					$ 71,000,000
Debt Instrument, Convertible, Difference Between Fair Value and Carrying Value					$ 57,200,000
Share Price | $ / shares					$ 14.25
Fair Value Assumptions, Weighted Average Volatility Rate					51.00%
Debt Instrument, Maturity Date, Percentage of Conversion Rate,	120.00%
Gain (Loss) on Extinguishment of Debt					$ (3,501,000)	$ (2,250,000)
Debt Instrument, Unamortized Discount					8,988,000	$ 10,572,000
Long-term Debt					147,078,000
Fenner Valley Farms LLC [Member]
Lease Term			99 years
Area of Real Estate Property | a			2,100
Long-term Debt			$ 12,000,000
Termination Period After Lease Effective Date			20 years
Lease Compounded Annual Return, Percentage			10.00%
Minimum Future Payments from Leases Held for Investment			$ 14,400,000
Reimbursement of Water Related Infrastructure from Leased Property, Annual Percentage			8.00%
Maximum Reimbursement of Pipeline Related Development Expenses from Leased Property			$ 3,000,000
Leased Property, Sale Price			1
Legal Fees			$ 490,000
Warrants [Member] | Interest Expense [Member]
Unrealized Gain (Loss) on Derivatives					$ 2,600,000
2017 Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares	362,500				362,500
Warrants and Rights Outstanding	$ 2,900,000				$ 2,900,000
Warrant Term	5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 14.94
Senior Secured Debt [Member]
Debt Instrument, Fee Amount	$ 60,000,000
Debt Instrument, Additional Amount after Refinance	$ 15,000,000			$ 15,000,000
Debt Instrument, Maturity Date, Description	The New Senior Secured Debt will mature on the earliest of (a) the four year anniversary of the Closing Date, and (b) the “Springing Maturity Date”, which is defined as the date which is 91 days prior to the maturity date of the 7.00% Convertible Senior Notes of Cadiz due 2020 (the “New Convertible Notes”) that were issued in December 2015 and April 2016 pursuant to the New Convertible Notes Indenture as defined in the Credit Agreement, if on the 91st day preceding the maturity date of the New Convertible Notes, the 5-Day VWAP, as defined in the Credit Agreement, is less than 120% of the then applicable Conversion Rate, as defined in the New Convertible Notes Indenture, and at least $10,000,000 in original principal amount of the New Convertible Notes is outstanding ((a) or (b), as applicable, the “Maturity Date”).
Debt Instrument, Maturity Date, Minimum Principal Outstanding Amount	$ 10,000,000
Debt Instrument, Payment-in-kind Rate	6.00%
Debt Instrument, Cash Rate	2.00%
Upfront Fee, Recorded as Additional Debt Discount, Percentage	2.00%
Senior Secured Debt [Member] | Legal and Finders fees [Member]
Debt Instrument, Unamortized Discount	$ 1,500,000
Prior Senior Secured Debt [Member]
Extinguishment of Debt, Amount	45,000,000			$ 45,000,000
Gain (Loss) on Extinguishment of Debt	$ (3,500,000)
2020 Convertible Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage	7.00%
2020 Convertible Senior Notes [Member] | Investors [Member]
Debt Instrument, Convertible, Conversion Price | $ / shares							$ 6.75
Debt Instrument, Fee Amount		$ 400,000
Debt Instrument, Interest Rate, Stated Percentage		7.00%
Debt Instrument, Unamortized Discount		$ 2,000,000
Unsecured Debt		10,000,000
Proceeds from Issuance of Debt		8,000,000
Debt Instrument, Convertible, Beneficial Conversion Feature		$ 1,480,000
Minimum [Member]
Debt Instrument, Convertible, Conversion Price | $ / shares					$ 6.75
Maximum [Member]
Debt Instrument, Convertible, Conversion Price | $ / shares					$ 8.05