Natural gas, NGLs and oil sales revenues are generally recognized when control of the product is transferred to the customer and collectability is reasonably assured.

We have three material revenue streams in our business: natural gas sales, NGLs sales and oil sales. Revenues on sales of natural gas, NGLs, oil and purchased natural gas and NGLs are recognized when control of the product is transferred to the purchaser and payment can be reasonably assured. Sales prices are negotiated based on factors normally considered in the industry, such as index or spot price, distance from the well to the pipeline or market, commodity quality and prevailing supply and demand conditions. We enter into purchase transactions with third parties and separate sale transactions to make use of unused gas pipeline capacity commitments. Revenues and expenses from these transactions are presented on a gross basis as we act as a principal in the transaction by assuming control of the commodities purchased and the responsibility to deliver the commodities sold. The majority of our product sale commitments are short-term in nature with a contract term of one year or less. Our product sales that have a contractual term greater than one year have no long-term fixed consideration. Accounts receivable attributable to our revenue contracts with customers was $209.1 million at September 30, 2019 and $438.3 million at December 31, 2018. Revenue attributable to each of our identified revenue streams is disaggregated below (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
		2019			2018			2019		2018
Natural gas sales	$	284,980		$	390,656		$	1,063,323	$	1,182,580
NGLs sales		143,195			278,563			508,035		705,793
Oil sales		46,579			67,212			138,629		206,077
Total natural gas, NGLs and oil sales		474,754			736,431			1,709,987		2,094,450
Sales of purchased natural gas		70,404			105,840			293,209		255,134
Sales of purchased NGLs		(183	)		(154	)		1,425		879
Other marketing revenue		2,794			3,699			9,200		11,435
Total	$	547,769		$	845,816		$	2,013,821	$	2,361,898