Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Line Items]

Property, Plant and Equipment [Table Text Block]

Depreciation is calculated primarily using the straight-line method over the following estimated useful lives:

Pipelines and related facilities	10 – 31 years
Storage and terminal facilities	10 – 25 years
Natural gas gathering and processing facilities	10 – 31 years
Trucking equipment and other	3 – 7 years
Office property and equipment	3 – 31 years

Property, plant and equipment consists of the following (in thousands):

	December 31,
	2017			2016
Land	$	273,168		$	90,337
Pipelines and related facilities	926,799			398,053
Storage and terminal facilities	1,111,001			279,506
Natural gas gathering and processing facilities	940,130			874,704
Linefill	25,747			25,804
Trucking equipment and other	45,162			45,417
Office property and equipment	63,052			61,146
Construction-in-progress	374,914			380,740
Property, plant and equipment, gross	3,759,973			2,155,707
Accumulated depreciation	(444,842		)	(393,635		)
Property, plant and equipment, net	$	3,315,131		$	1,762,072