Acquisitions - Hawaii Refinery Expansion (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended	6 Months Ended
	Dec. 19, 2018	Mar. 31, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Issuance of common stock for business combination		$ 36,980	$ 37,000
Hawaii Refinery Expansion - Asset Acquisition
Business Acquisition [Line Items]
Consideration transferred	$ 66,900
Consideration transferred, working capital adjustments	4,300
Payments for asset acquisitions	47,600
Issuance of common stock for business combination	19,300
Property, plant and equipment, additions	45,200
Asset acquisition, non-hydrocarbon inventory	4,300
Asset acquisition, hydrocarbon inventory	$ 17,400
Common Stock
Business Acquisition [Line Items]
Common stock offering, net of issuance costs (in shares)		2,364
Issuance of common stock for business combination		$ 23
Common Stock | Hawaii Refinery Expansion - Asset Acquisition
Business Acquisition [Line Items]
Common stock offering, net of issuance costs (in shares)	1,100