Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, plant and equipment, net	$ 1,962,580	$ 1,959,578
Construction-in-process	266,083	261,690
Finance leases right of use	$ 14,433
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	50,752,101	50,699,781
Common stock, shares outstanding (in shares)	50,752,101	50,699,781
Senior Secured Notes [Member]
Deferred financing costs	$ 7,149	$ 7,434
Other Loans, Limited and Non-recourse [Member]
Deferred financing costs	9,262	9,354
Senior Unsecured Bonds [Member]
Deferred financing costs	706	758
Other Loans, Full Recourse [Member]
Deferred financing costs	1,483	921
Variable Interest Entity, Primary Beneficiary [Member]
Property, plant and equipment, net	1,843,823	1,859,228
Construction-in-process	110,907	$ 104,085
Finance leases right of use	$ 8,396