Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

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,
	2016			2015
Land	$	90,337		$	89,815
Pipelines and related facilities	398,053			338,789
Storage and terminal facilities	279,506			283,608
Natural gas gathering and processing facilities	874,704			810,358
Linefill	25,804			26,900
Trucking equipment and other	45,417			43,157
Office property and equipment	61,146			45,818
Construction-in-progress	380,740			248,145
Property, plant and equipment, gross	2,155,707			1,886,590
Accumulated depreciation	(393,635		)	(319,769		)
Property, plant and equipment, net	$	1,762,072		$	1,566,821