Nature of operations and summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

Components of Accounts Receivable

Accounts receivable consisted of the following at December 31:

	2013			2012
Joint interests	$	31,335		$	19,282
Accrued commodity sales	60,768			50,814
Derivative settlements	4,616			8,013
Other	1,392			472
Allowance for doubtful accounts	(1,596		)	(1,274		)
	$	96,515		$	77,307

Components of Inventories

Inventories consisted of the following at December 31:

	2013			2012
Equipment inventory	$	13,657		$	8,047
Commodities	3,186			3,175
Inventory valuation allowance	(706		)	(712		)
	$	16,137		$	10,510

Schedule Of Estimated Useful Lives for Property and Equipment

Estimated useful lives of our assets are as follows:

Furniture and fixtures			10 years
Automobiles and trucks			5 years
Machinery and equipment	10	—	20 years
Office and computer equipment	5	—	10 years
Building and improvements	10	—	40 years