Note 4 - Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2019	[1]	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	[1]	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 20,177		$ 65,684	$ 70,864	$ 48,501	$ 65,513	$ 81,422	$ 88,336	$ 55,747		$ 205,226	$ 291,018	$ 275,026
Revenue from non-contractual arrangements											222	222
BTC rebate											(39,423)	(13,559)
Bill and Hold Revenue [Member]
Revenue											51,700	44,924
Non-bill and Hold Revenue [Member]
Revenue											153,526	246,094
Long-term Contract Revenue [Member]
Revenue											40,156	60,721
Short-term Contract Revenue [Member]
Revenue											$ 204,271	$ 243,634

[1] The fourth quarter of 2019 and the first quarter of 2018 includes the retroactive reinstatement of the BTC in revenue and gross profit (see Note 3 for further information).