Accumulated Other Comprehensive Income (Tables)

6 Months Ended

Jun. 30, 2019

Accumulated Other Comprehensive Income [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The following table presents the changes in the components of accumulated other comprehensive loss for the periods shown (in thousands):

	Three Months Ended June 30, 2019
	Currency Translation			Employee Benefit Plans			Total			Attributable to Noncontrolling Interest		Attributable to SemGroup
March 31, 2019	$	(60,435	)	$	(5,045	)	$	(65,480	)	$	5,580	$	(71,060	)
Currency translation adjustment, net of income tax expense of $8,481	27,287			—			27,287			7,969		19,318
Changes related to benefit plans, net of income tax expense of $37	—			100			100			49		51
June 30, 2019	$	(33,148	)	$	(4,945	)	$	(38,093	)	$	13,598	$	(51,691	)

	Three Months Ended June 30, 2018
	Currency Translation			Employee Benefit Plans			Total
March 31, 2018	$	(32,846	)	$	(2,784	)	$	(35,630	)
Currency translation adjustment, net of income tax benefit of $5,123	(15,863		)	—			(15,863		)
Currency translation adjustment reclassified to gain on disposal, net of income tax expense of $7,117	22,041			—			22,041
Changes related to benefit plans, net of income tax expense of $0	—			2			2
June 30, 2018	$	(26,668	)	$	(2,782	)	$	(29,450	)

	Six Months Ended June 30, 2019
	Currency Translation			Employee Benefit Plans			Total			Attributable to Noncontrolling Interest		Attributable to SemGroup
December 31, 2018	$	(45,816	)	$	(5,431	)	$	(51,247	)	$	—	$	(51,247	)
Currency translation adjustment, net of income tax expense of $7,311	23,552			—			23,552			13,581		9,971
Reclassification of certain tax effects from adoption of ASU 2018-02	(10,884		)	—			(10,884		)	—		(10,884		)
Changes related to benefit plans, net of income tax expense of $180	—			486			486			17		469
June 30, 2019	$	(33,148	)	$	(4,945	)	$	(38,093	)	$	13,598	$	(51,691	)

	Six Months Ended June 30, 2018
	Currency Translation			Employee Benefit Plans			Total
December 31, 2017	$	(51,014	)	$	(2,787	)	$	(53,801	)
Currency translation adjustment, net of income tax benefit of $8,073	(25,000		)	—			(25,000		)
Currency translation adjustment reclassified to gain (loss) on disposal, net of income tax expense of $15,935	49,346			—			49,346
Changes related to benefit plans, net of income tax expense of $1	—			5			5
June 30, 2018	$	(26,668	)	$	(2,782	)	$	(29,450	)