Note 2 - Summary of Significant Accounting Policies - Credit Concentration (Details) - Customer Concentration Risk [Member]	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Customer A [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	14.00%	10.00%
Customer G [Member] | Accounts Receivable [Member]
Credit concentration	12.00%	10.00%
Customer B [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	11.00%	10.00%
Customer H [Member] | Accounts Receivable [Member]
Credit concentration	10.00%	25.00%
Customer C [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	10.00%	10.00%
Customer I [Member] | Accounts Receivable [Member]
Credit concentration	10.00%	11.00%
Customer D [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	10.00%	43.00%
Customer E [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	10.00%	10.00%
Customer F [Member] | Revenue from Contract with Customer Benchmark [Member]
Credit concentration	10.00%	26.00%