Accumulated Other Comprehensive Income (Tables)

9 Months Ended

Sep. 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 September 30, 2019
	Currency Translation			Employee Benefit Plans			Total			Attributable to Noncontrolling Interest			Attributable to SemGroup
June 30, 2019	$	(33,148	)	$	(4,945	)	$	(38,093	)	$	13,598		$	(51,691	)
Currency translation adjustment, net of income tax benefit of $597	(6,424		)	—			(6,424		)	(4,519		)	(1,905		)
Changes related to benefit plans, net of income tax expense of $39	—			107			107			(86		)	193
September 30, 2019	$	(39,572	)	$	(4,838	)	$	(44,410	)	$	8,993		$	(53,403	)

	Three Months Ended September 30, 2018
	Currency Translation			Employee Benefit Plans			Total
June 30, 2018	$	(26,668	)	$	(2,782	)	$	(29,450	)
Currency translation adjustment, net of income tax expense of $1,081	3,349			—			3,349
Changes related to benefit plans, net of income tax expense of $1	—			3			3
September 30, 2018	$	(23,319	)	$	(2,779	)	$	(26,098	)

	Nine Months Ended September 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 $2,526	17,128			—			17,128			9,062			8,066
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 $219	—			593			593			(69		)	662
September 30, 2019	$	(39,572	)	$	(4,838	)	$	(44,410	)	$	8,993		$	(53,403	)

	Nine Months Ended September 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 $6,992	(21,651		)	—			(21,651		)
Currency translation adjustment reclassified to gain 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 $2	—			8			8
September 30, 2018	$	(23,319	)	$	(2,779	)	$	(26,098	)