Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	May 01, 2018	Dec. 31, 2017
Purchase Price
Goodwill			$ 273,524	$ 261,340		$ 272,079
EPMH
Purchase Price
Accounts receivable, net		$ 43,305		43,305
Inventories		86,112		86,112
Property, plant and mine development		146,558		148,495
Mineral rights		408,889		419,469
Identifiable intangible assets - finite lived		8,770		10,270	$ 8,770
Identifiable intangible assets - indefinite lived		36,800		38,050
Prepaids and deposits		1,827		2,072
Other non-current assets		7,474		7,474
Goodwill		162,812		150,628
Total assets acquired		902,547		905,875
Accounts payable		13,435		13,435
Accrued expenses and other current liabilities		10,304		10,304
Deferred tax liabilities		119,483		122,811
Other long term liabilities		16,076		16,076
Total liabilities assumed		159,298		162,626
Net assets acquired		743,249		743,249
Measurement Period Adjustments
Accounts receivable, net		0
Inventories		0
Property, plant and mine development		(1,937)
Mineral rights		(10,580)
Identifiable intangible assets - finite lived		(1,500)
Identifiable intangible assets - indefinite lived		(1,250)
Prepaids and deposits		(245)
Other assets		0
Goodwill		12,184	$ 12,184
Total assets acquired		(3,328)
Accounts payable		0
Accrued expenses and other current liabilities		0
Deferred tax liabilities		(3,328)
Long term obligations		0
Total liabilities assumed		(3,328)
Net assets acquired		$ 0
MS Sand
Purchase Price
Accounts receivable, net	$ 11,201					11,201
Inventories	8,067					8,067
Other current assets	362					362
Assets held for sale	9,453					9,453
Property, plant and mine development	27,458					27,458
Mineral rights	23,500					26,300
Identifiable intangible assets - finite lived	1,840					1,840
Other non-current assets	1,136					1,136
Goodwill	25,322					22,522
Total assets acquired	108,339					108,339
Accounts payable and accrued expenses	3,761					3,761
Unfavorable leasehold positions	2,237					2,237
Notes Payable	866					866
Asset retirement obligations	474					474
Other long term liabilities	0					0
Total liabilities assumed	7,338					7,338
Net assets acquired	101,001					$ 101,001
Measurement Period Adjustments
Accounts receivable, net	0
Inventories	0
Other current assets	0
Assets held for sale	0
Property, plant and mine development	0
Mineral rights	(2,800)
Identifiable intangible assets - finite lived	0
Other assets	0
Goodwill	2,800			$ 2,800
Total assets acquired	0
Accounts payable and accrued expenses	0
Unfavorable leasehold positions	0
Notes Payable	0
Other long term liabilities	0
Asset retirement obligations	0
Total liabilities assumed	0
Net assets acquired	$ 0