Supplemental Cash Flow Information - Operating assets and liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Components of operating assets and liabilities
Decrease (increase) in restricted cash	$ 0	$ 33
Decrease (increase) in accounts receivable	21,412	(14,835)
Decrease (increase) in receivable from affiliates	48	793
Decrease (increase) in inventories	(17,968)	57,530
Decrease (increase) in other current assets	(6,960)	(4,007)
Decrease (increase) in other assets	4,298	(3,131)
Increase (decrease) in accounts payable and accrued liabilities	(34,502)	(37,453)
Increase (decrease) in payable to affiliates	(2,845)	(5,619)
Increase (decrease) in other noncurrent liabilities	5,374	(3,637)
Total changes in operating assets and liabilities	$ (31,143)	$ (10,326)