Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Changes in the allowance for doubtful accounts

The following table presents our allowance for doubtful accounts activity for the periods indicated (in thousands):

	Year Ended December 31,
	2017			2016			2015
Balance at beginning of period	$	225		$	206		$	179
Charges to costs and expenses	137			100			116
Deductions	(59		)	(81		)	(89		)
Balance at end of period	$	303		$	225		$	206

Schedule of cost of retirement plans

Our 401(k) plan contributory expenses were as follows for the periods indicated (in thousands):

	Year Ended December 31,
	2017		2016		2015
Contributory expenses	$	734	$	757	$	768

Reporting revenue of crude oil contracts on a gross revenue basis

Reporting these crude oil contracts on a gross revenue basis would increase our reported revenues as follows for the periods indicated (in thousands):

	Year Ended December 31,
	2017		2016		2015
Revenue gross-up	$	203,095	$	314,270	$	480,111