Revenue (Tables)

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following tables disaggregate the Company’s coal revenues by product category and by market to depict how the nature, amount, timing, and uncertainty of the Company’s coal revenues and cash flows are affected by economic factors:

	Three Months Ended September 30, 2019
	Met		Thermal		Total
Export coal revenues	$	248,628	$	13,187	$	261,815
Domestic coal revenues	137,146		125,026		262,172
Total coal revenues	$	385,774	$	138,213	$	523,987

	Three Months Ended September 30, 2018
	Met		Thermal		Total
Export coal revenues	$	371,749	$	12,848	$	384,597
Domestic coal revenues	15,292		43,116		58,408
Total coal revenues	$	387,041	$	55,964	$	443,005

	Nine Months Ended September 30, 2019
	Met		Thermal		Total
Export coal revenues	$	928,390	$	39,569	$	967,959
Domestic coal revenues	429,457		387,359		816,816
Total coal revenues	$	1,357,847	$	426,928	$	1,784,775

	Nine Months Ended September 30, 2018
	Met		Thermal		Total
Export coal revenues	$	1,239,008	$	28,634	$	1,267,642
Domestic coal revenues	38,156		140,740		178,896
Total coal revenues	$	1,277,164	$	169,374	$	1,446,538

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction

The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied as of September 30, 2019.

	Remainder of 2019		2020		2021		2022		2023		2024		Total
Estimated coal revenues	$	64,916	$	357,281	$	196,240	$	138,444	$	130,267	$	46,000	$	933,148

Contract with Customer, Liability

The following table includes the opening and closing balances of contract assets from modifications with contracts with customers, which are included within prepaid expenses and other current assets on the Company’s Condensed Consolidated Balance Sheets:

	September 30, 2019		December 31, 2018
Contract assets (1)	$	985	$	950

⁽¹⁾ Amounts primarily relate to payments made upon modification of coal contracts.