Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2020

Commitments and Contingencies Disclosure [Abstract]

Schedule of current maturities of contractual obligation

Aggregate future minimum payments under these obligations in effect at September 30, 2020 are as follows (in thousands):

Year ended December 31:	Capital Spend Commitments		Minimum Purchase Commitments(a)
Remainder of 2020	$	3,175	$	4,307
2021	—		1,129
2022	—		98
2023	—		8
2024	—		—
Thereafter	—		—
	$	3,175	$	5,542

a.     Included in these amounts are sand purchase commitments of $4.0 million. Pricing for certain sand purchase agreements is variable and, therefore, the total sand purchase commitments could be as much as $4.7 million.

Schedule of letters of credit

The letters of credit are categorized below (in thousands):

	September 30,		December 31,
	2020		2019
Environmental remediation	$	4,477	$	4,182
Insurance programs	4,105		4,105
Rail car commitments	455		455
Total letters of credit	$	9,037	$	8,742