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Fair Value Measurements

6 Months Ended

Jun. 30, 2025

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.FAIR VALUE MEASUREMENTS

​

The following table summarizes certain fair value measurements within the hierarchy:

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​

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​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Fair Value

​

​

Carrying Value

Level 1

Level 2

Level 3

​

​

(in thousands)

​

June 30, 2025

​

​

​

​

​

​

​

​

​

​

​

​

​

Recorded on a recurring basis:

​

​

​

​

​

​

​

​

​

​

​

​

​

Digital assets

​

$

58,030

​

$

58,030

​

$

—

​

$

—

​

Contingent consideration

​

$

10,677

​

$

—

​

$

—

​

$

10,677

​

Debt securities

​

$

13,046

​

$

—

​

$

—

​

$

13,046

​

Additional disclosures:

​

​

​

​

​

​

​

​

​

​

​

​

​

Long-term debt

​

$

477,054

​

$

—

​

$

510,517

​

$

—

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

December 31, 2024

​

​

​

​

​

​

​

​

​

​

​

​

​

Recorded on a recurring basis:

​

​

​

​

​

​

​

​

​

​

​

​

​

Digital assets

​

$

45,037

​

$

45,037

​

$

—

​

$

—

​

Contingent consideration

​

$

13,100

​

$

—

​

$

—

​

$

13,100

​

Additional disclosures:

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​

​

​

​

​

​

​

​

​

​

​

​

Long-term debt

​

$

490,387

​

$

—

​

$

523,461

​

$

—

​

​

The carrying amounts for cash equivalents, accounts receivable, accounts payable, accrued and other liabilities approximate fair value due to the short maturity of those instruments.

​

The fair value of our digital assets is based on an exchange quoted price.  See Note 6 – Digital Assets for more information on our digital assets.

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The fair value measurement of our contingent consideration liability is determined using an option approach methodology simulation based on significant inputs not observable in active markets representing a Level 3 fair value measurement under the fair value hierarchy. Our contingent consideration liability is associated with our acquisition of our Hamilton County Coal, LLC (“Hamilton”) mine in 2015 wherein we agreed to pay the seller additional consideration for the acquisition if the average quarterly sales price exceeds a defined threshold price in any future quarters subject to a maximum of $110.0 million reduced for any payments made under an overriding royalty agreement with the sellers relating to mineral interests controlled by our Hamilton mine. We have paid $14.1 million under this contingent consideration agreement and $0.3 million under the overriding royalty agreement as of June 30, 2025.

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The fair value measurement of our debt securities is determined using a combination of market approaches and option-pricing models which utilize significant inputs not observable in active markets representing a Level 3 fair value measurement under the fair value hierarchy. See Note 7 – Investments for additional information on our debt securities.

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The estimated fair value of our long-term debt, including current maturities, is based on interest rates that we believe are currently available to us in active markets for issuance of debt with similar terms and remaining maturities. See Note 8 – Long-Term Debt for additional information on our long-term debt.

​

Quantitative Information about Level 3 Fair Value Measurements

​

Contingent Consideration

​

Our option approach methodology simulation for contingent consideration generates an expected payment for each quarter in Hamilton’s mine life by using proprietary internal estimates of our uncommitted coal sales prices and generating a simulated uncommitted coal sales price by applying unobservable inputs through a million simulations. This simulated coal sales price is then used in a calculation of the expected future payments using our proprietary committed coal sales prices and production for each quarter. We then calculate the present value of the estimated future payments. The following table presents quantitative information about certain significant unobservable inputs used in the fair value measurement for our contingent consideration liability. The use of significant unobservable inputs results in uncertainty as of the reporting date, as changes in these unobservable inputs could significantly raise or lower the estimated fair value.

​

​	​	​	​	​	​	​	​
​		Valuation Technique(s)		Unobservable Input		Range/Amount (Average) (a)	​
​	​	​	​	​	​	​	​
June 30, 2025	​	​	​	​	​	​	​
​	​	​	​	​	​	​	​
Contingent Consideration	​	Option approach methodology simulation	​	Cost of Debt	​	6.51% - 8.56%	​
​	​	​	​	Coal price volatility	​	6.2%	​
​	​	​	​	Market price of risk adjustment (annual)	​	6.2%	​
December 31, 2024	​	​	​	​	​	​	​
​	​	​	​	​	​	​	​
Contingent Consideration	​	Option approach methodology simulation	​	Cost of Debt	​	6.51% - 8.56%	​
​	​	​	​	Coal price volatility	​	6.2%	​
​	​	​	​	Market price of risk adjustment (annual)	​	6.2%	​
​	​	​	​	​	​	​	​
(a) Averages represent the arithmetic average of the inputs and is not weighted by a relative fair value or notional amount							​

​

The following table represents changes in our contingent consideration liability:

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​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Three Months Ended

​

Six Months Ended

​

​

​

June 30,

​

June 30,

​

​

2025

2024

2025

​

2024

​

​

(in thousands)

​

Beginning balance

​

$

11,324

​

$

8,469

​

$

13,100

​

$

9,900

​

Noncash changes in fair value (1)

​

​

2,005

​

​

—

​

​

2,005

​

​

—

​

Payments

​

​

(2,652)

​

​

(2,380)

​

​

(4,428)

​

​

(3,811)

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Ending balance

​

$

10,677

​

$

6,089

​

$

10,677

​

$

6,089

​

(1) Noncash changes in the fair value of our continent consideration liability are included in the Operating expenses (excluding depreciation, depletion and amortization) line item within our condensed consolidated statements of income.

​

Debt Securities

​

The fair value of our debt securities is determined using a combination of market approaches and option-pricing models. The underlying enterprise value is estimated using income and market approaches which utilize discounted cash flows and market participant values for assets in hypothetical sales scenarios. The enterprise value is then utilized in market approach models and option-pricing models taking into account the rights and preferences of the convertible notes, expected exit scenarios, and volatility associated with such outcomes to arrive at a fair value. The following table presents quantitative information about certain significant unobservable inputs used in the fair value measurement. The use of significant unobservable inputs results in uncertainty as of the reporting date, as changes in these unobservable inputs could significantly raise or lower the estimated fair value.

​

​	​	​	​	​	​	​	​
​		Valuation Technique(s)		Unobservable Input		Range/Amount (Average) (a)	​
​	​	​	​	​	​	​	​
June 30, 2025	​	​	​	​	​	​	​
​	​	​	​	​	​	​	​
Debt securities	​	Option-pricing approach methodology	​	Industry volatility	​	29.10% - 70.86% (49.98%)	​
​	​	​	​	Estimated time to exit	​	2.0 - 4.0 (3.0) years	​
​	​	Income approach methodology	​	Forecasted future cash flow	​	$906.6 - $1,285.9 ($1,096.3) million	​
​	​	​	​	Cost of capital	​	11.25% - 16.58% (13.92%)	​
​	​	​	​	​	​	​	​
(a) Averages represent the arithmetic average of the inputs and is not weighted by a relative fair value or notional amount							​

​

The following table represents changes in our debt securities:

​

​	​	​	​	​	​	​	​
​	​	Three Months Ended		​	Six Months Ended		​
​	​	June 30,		​	June 30,		​
​		2025			2025
​	​	(in thousands)					​
Beginning balance	​	$	—	​	$	—	​
Noncash changes in fair value (1)	​	​	10,919	​	​	10,919	​
Payments	​	​	2,127	​	​	2,127	​
Ending balance	​	$	13,046	​	$	13,046	​

(1) Noncash changes in the fair value of our debt securities are included in the Change in unrealized gains (losses) on debt securities line item within our condensed consolidated statements of comprehensive income.

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- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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