Note 7 - Revenue 2 (Details Textual) $ in Millions	Jun. 30, 2021 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01 | Fixed-price Contract [Member]
Revenue, Remaining Performance Obligation, Amount	$ 408
Revenue, Remaining Performance Obligation, Percentage	74.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	1 year 6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Contracts with Price Reopeners [Member]
Revenue, Remaining Performance Obligation, Amount	$ 237
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	6 years