Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Jun. 30, 2018	May 01, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 414,257		$ 272,079
EPMH
Business Acquisition [Line Items]
Accounts receivable, net		$ 43,354
Inventories		84,395
Property, plant and mine development		123,086
Mineral rights		462,050
Identifiable intangible assets - finite lived		21,050
Identifiable intangible assets - indefinite lived		25,050
Prepaids and deposits		2,054
Other non-current assets		4,089
Goodwill		139,378
Total assets acquired		904,506
Accounts payable and accrued expenses		13,435
Accrued expenses and other current liabilities		8,255
Deferred tax liabilities		130,209
Other long term liabilities		9,766
Total liabilities assumed		161,665
Net assets acquired		$ 742,841
MS Sand
Business Acquisition [Line Items]
Accounts receivable, net			11,201
Inventories			8,067
Property, plant and mine development			27,458
Mineral rights			23,500
Identifiable intangible assets - finite lived			1,840
Other current assets			362
Assets held for sale			9,453
Other non-current assets			1,136
Goodwill			25,322
Total assets acquired			108,339
Accounts payable and accrued expenses			3,761
Unfavorable leasehold positions			2,237
Notes Payable			866
Other long term liabilities			0
Asset retirement obligations			474
Total liabilities assumed			7,338
Net assets acquired			101,001
MS Sand | Estimate as of December 31, 2017
Business Acquisition [Line Items]
Accounts receivable, net			11,201
Inventories			8,067
Property, plant and mine development			27,458
Mineral rights			26,300
Identifiable intangible assets - finite lived			1,840
Other current assets			362
Assets held for sale			9,453
Other non-current assets			1,136
Goodwill			22,522
Total assets acquired			108,339
Accounts payable and accrued expenses			3,761
Unfavorable leasehold positions			2,237
Notes Payable			866
Other long term liabilities			0
Asset retirement obligations			474
Total liabilities assumed			7,338
Net assets acquired			101,001
MS Sand | Measurement Period Adjustments
Business Acquisition [Line Items]
Accounts receivable, net			0
Inventories			0
Property, plant and mine development			0
Mineral rights			(2,800)
Identifiable intangible assets - finite lived			0
Other current assets			0
Assets held for sale			0
Other non-current assets			0
Goodwill			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