Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee	$ 13,951	$ 12,614
Revenues	567,232	661,609
Depreciation and amortization	59,036	50,536
Gain (Loss) on Disposition of Assets	(1,444)	(3,566)
Income tax expense (benefit)	(4,606)	23,083
Segment profit	124,132	115,409
EBITDA Adjustment to Equity Earnings	4,710	4,883
Net unrealized loss (gain) related to commodity derivative instruments	4,818	2,226
General and Administrative Expense	29,547	26,477
Interest Expense	36,652	42,461
Foreign currency transaction loss (gain)	(288)	3,294
Other expense (income), net	(979)	(950)
Net loss	(3,314)	(33,035)
Total assets	6,374,038		$ 5,210,307
Equity method investments	276,893		274,009
U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee	13,937	12,605
Revenues	473,468	522,945
U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	48,937	52,256
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	44,827	45,145
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee	14	9
Revenues	0	41,263
Depreciation and amortization	671	742
Income tax expense (benefit)	(4,960)	19,904
Segment profit	(237)	10,963
Total assets	360,788		119,668
Equity method investments	18,979		18,966
Operating Segments [Member] | U.S. Liquids [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	39,487	34,107
Income tax expense (benefit)	147	209
Segment profit	89,511	68,056
Total assets	4,005,344		3,689,384
Equity method investments	257,914		255,043
Operating Segments [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	11,095	10,449
Segment profit	12,165	14,277
Total assets	703,069		716,837
Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	7,783	5,238
Income tax expense (benefit)	207	2,970
Segment profit	22,693	22,113
Total assets	1,304,837		$ 684,418
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(4,289)	(3,640)
Intersegment Eliminations [Member] | U.S. Gas [Member]
Segment Reporting Information [Line Items]
Revenues	$ 4,289	$ 3,640