Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Long-term Purchase Commitment [Line Items]

Summary of Changes in Asset Retirement Obligations

The following table summarizes the changes in this liability from December 31, 2015 through December 31, 2018 (in thousands):

Balance, December 31, 2015	$	15,946
Accretion	2,292
Payments made	(159		)
Currency translation adjustments	469
Balance, December 31, 2016	18,548
Accretion	2,812
Payments made	(160		)
Currency translation adjustments	1,404
Balance, December 31, 2017	22,604
Accretion	4,070
Payments made	(3,111		)
Currency translation adjustments	(1,820		)
Balance, December 31, 2018	$	21,743

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Future minimum payments required under operating leases that have initial or remaining non-cancellable lease terms in excess of one year at December 31, 2018, are as follows (in thousands): 

For year ending:
December 31, 2019	$	5,795
December 31, 2020	5,796
December 31, 2021	5,312
December 31, 2022	3,455
December 31, 2023	2,453
Thereafter	40,551
Total future minimum lease payments	$	63,362

Summary of Purchase and Sale Commitments [Table Text Block]

At December 31, 2018, such commitments included the following (in thousands):

	Volume (barrels)	Value
Fixed price purchases	4,626	$	230,562
Fixed price sales	4,920	$	246,755
Floating price purchases	14,638	$	750,711
Floating price sales	17,290	$	830,407

Long-term Purchase Commitment [Table Text Block]

Our U.S. Liquids segment has minimum volume commitments for pipeline transportation of crude oil. At December 31, 2018, the approximate amount of future obligations is as follows (in thousands):

For year ending:
December 31, 2019	$	21,865
December 31, 2020	19,751
December 31, 2021	12,976
December 31, 2022	13,231
December 31, 2023	13,496
Thereafter	6,816
Total expected future payments	$	88,135

Our U.S. Gas segment has a take or pay contractual obligation related to the fractionation of natural gas liquids through June 2023. At December 31, 2018, the approximate amount of future obligations is as follows (in thousands):

For year ending:
December 31, 2019	$	9,783
December 31, 2020	9,063
December 31, 2021	7,337
December 31, 2022	6,905
December 31, 2023	2,854
Thereafter	—
Total expected future payments	$	35,942