Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Earnings from equity method investments	$ 12,695	$ 14,351	$ 26,646	$ 26,965
Revenues	674,940	595,794	1,242,172	1,257,403
Depreciation and amortization	64,011	51,755	123,047	102,291
Loss (gain) on Disposal or Impairment	8,936	1,824	7,492	(1,742)
Income tax expense (benefit)	(6,085)	(3,613)	(10,691)	19,470
Segment profit	125,679	117,106	249,811	232,515
EBITDA Adjustment to Equity Earnings	4,718	4,886	9,428	9,769
Net unrealized loss related to commodity derivative instruments	4,903	4,409	9,721	6,635
General and Administrative Expense	25,520	22,886	55,067	49,363
Interest Expense	38,910	35,904	75,562	78,365
Foreign currency transaction loss (gain)	(989)	2,314	(1,277)	5,608
Other expense (income), net	(1,347)	(533)	(2,326)	(1,483)
Net loss	(12,898)	(2,726)	(16,212)	(35,761)
Total assets	6,257,940		6,257,940		$ 5,210,307
Equity method investments	284,186		284,186		274,009
U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Earnings from equity method investments	12,688	14,338	26,625	26,943
Revenues	575,033	466,133	1,048,501	989,078
U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	37,083	59,167	86,020	111,406
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	62,824	69,631	107,651	114,776
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earnings from equity method investments	7	13	21	22
Revenues	0	863	0	42,143
Depreciation and amortization	739	747	1,410	1,473
Income tax expense (benefit)	4,765	(6,930)	(195)	12,974
Segment profit	(219)	(172)	(456)	10,791
Total assets	307,813		307,813		119,668
Equity method investments	18,986		18,986		18,966
Operating Segments [Member] | U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	39,824	34,922	79,311	69,045
Income tax expense (benefit)	149	181	296	390
Segment profit	85,189	80,393	174,700	148,449
Total assets	3,882,840		3,882,840		3,689,384
Equity method investments	265,200		265,200		255,043
Operating Segments [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	11,112	10,822	22,207	21,271
Segment profit	11,040	15,437	23,205	29,714
Total assets	686,633		686,633		716,837
Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	12,336	5,264	20,119	10,502
Income tax expense (benefit)	(10,999)	3,136	(10,792)	6,106
Segment profit	29,669	21,448	52,362	43,561
Total assets	1,380,654		1,380,654		$ 684,418
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(3,983)	(3,206)	(8,272)	(6,863)
Intersegment Eliminations [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	$ 3,983	$ 3,206	$ 8,272	$ 6,863