Note 3 - Revenue - Revenue (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Revenue		$ 330,760	$ 275,100
Coal Revenue [Member]
Revenue	[1]	285,535	255,452
Terminal Revenue [Member]
Revenue		18,212	16,501
Freight Revenue [Member]
Revenue		$ 27,013	$ 3,147

[1] For the three months ended March 31, 2021 and 2020, the PAMC segment had revenues from the following customers, each comprising over 10% of the Company's total sales: Three Months Ended March 31, 2021 2020 Customer A $ 57,680 $ 38,908 Customer B $ 33,239 $ 104,354 Customer C $ 36,599 $ 35,683 Customer D $ 44,236 *