Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Earnings from equity method investments	$ 9,065	$ 14,528	$ 35,711	$ 41,493
Revenues	562,410	633,996	1,804,582	1,891,399
Depreciation and amortization	61,489	53,598	184,536	155,889
Loss (gain) on Disposal or Impairment	(373)	(383)	7,119	(2,125)
Income tax expense (benefit)	(4,019)	(2,697)	(14,710)	16,773
Segment profit	114,573	114,884	364,384	347,399
EBITDA Adjustment to Equity Earnings	4,633	4,926	14,061	14,695
Net unrealized loss (gain) related to commodity derivative instruments	(10,742)	(4,860)	(1,021)	1,775
General and Administrative Expense	29,662	21,904	84,729	71,267
Interest Expense	39,663	35,318	115,225	113,683
Foreign currency transaction loss (gain)	801	(983)	(476)	4,625
Other expense (income), net	(1,075)	(400)	(3,401)	(1,883)
Net income (loss)	(5,466)	8,461	(21,678)	(27,300)
Total assets	6,112,630		6,112,630		$ 5,210,307
Equity method investments	283,638		283,638		274,009
U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Earnings from equity method investments	9,075	14,546	35,700	41,489
Revenues	457,672	520,287	1,506,173	1,509,365
U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	34,346	71,770	120,366	183,176
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	70,392	41,939	178,043	156,715
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earnings from equity method investments	(10)	(18)	11	4
Revenues	0	0	0	42,143
Depreciation and amortization	736	719	2,146	2,192
Income tax expense (benefit)	(6,700)	(5,742)	(6,895)	7,232
Segment profit	(1,527)	(913)	(1,983)	9,878
Total assets	292,657		292,657		119,668
Equity method investments	18,976		18,976		18,966
Operating Segments [Member] | U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	36,890	36,793	116,201	105,838
Income tax expense (benefit)	149	209	445	599
Segment profit	67,508	75,500	242,208	223,949
Total assets	3,742,432		3,742,432		3,689,384
Equity method investments	264,662		264,662		255,043
Operating Segments [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	10,958	10,836	33,165	32,107
Segment profit	13,661	19,754	36,866	49,468
Total assets	665,044		665,044		716,837
Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	12,905	5,250	33,024	15,752
Income tax expense (benefit)	2,532	2,836	(8,260)	8,942
Segment profit	34,931	20,543	87,293	64,104
Total assets	1,412,497		1,412,497		$ 684,418
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(3,082)	(4,705)	(11,354)	(11,568)
Intersegment Eliminations [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	$ 3,082	$ 4,705	$ 11,354	$ 11,568