Segment Information (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]
Midstream Services — Affiliate	$ 85,882	$ 66,924	$ 177,878	$ 131,187
Total Revenues	158,261	121,971	306,221	219,704
Income (Loss) Before Income Taxes	53,289	44,625	116,651	83,835
Additions to Long-Lived Assets	57,203	154,761	132,561	609,512
Additions to Investments	143,984	119	414,587	119
Total Assets	2,498,531		2,498,531		$ 1,997,917
Gathering Systems
Segment Reporting Information [Line Items]
Midstream Services — Affiliate	67,515	47,850	131,924	91,829
Total Revenues	137,440	99,796	254,004	173,343
Income (Loss) Before Income Taxes	49,133	29,066	96,719	59,894
Additions to Long-Lived Assets	55,850	149,571	130,656	596,960
Additions to Investments	0	0	0	0
Total Assets	1,911,769		1,911,769		1,804,100
Fresh Water Delivery
Segment Reporting Information [Line Items]
Midstream Services — Affiliate	18,367	19,074	45,954	39,358
Total Revenues	20,821	22,175	52,217	46,361
Income (Loss) Before Income Taxes	13,621	18,434	36,830	35,937
Additions to Long-Lived Assets	1,113	5,190	1,394	12,552
Additions to Investments	0	0	0	0
Total Assets	87,618		87,618		96,280
Investments in Midstream Entities
Segment Reporting Information [Line Items]
Midstream Services — Affiliate	0	0	0	0
Total Revenues	0	0	0	0
Income (Loss) Before Income Taxes	(1,748)	4,091	593	6,959
Additions to Long-Lived Assets	0	0	0	0
Additions to Investments	143,984	119	414,587	119
Total Assets	487,383		487,383		82,317
Corporate
Segment Reporting Information [Line Items]
Midstream Services — Affiliate	0	0	0	0
Total Revenues	0	0	0	0
Income (Loss) Before Income Taxes	(7,717)	(6,966)	(17,491)	(18,955)
Additions to Long-Lived Assets	240	0	511	0
Additions to Investments	0	0	0	0
Total Assets	11,761		11,761		$ 15,220
Midstream Services — Third Party
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	20,597	13,469	43,691	24,829
Midstream Services — Third Party | Gathering Systems
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	18,143	10,368	37,428	17,826
Midstream Services — Third Party | Fresh Water Delivery
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	2,454	3,101	6,263	7,003
Midstream Services — Third Party | Investments in Midstream Entities
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	0	0	0	0
Midstream Services — Third Party | Corporate
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	0	0	0	0
Crude Oil Sales — Third Party
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	51,782	41,578	84,652	63,688
Crude Oil Sales — Third Party | Gathering Systems
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	51,782	41,578	84,652	63,688
Crude Oil Sales — Third Party | Fresh Water Delivery
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	0	0	0	0
Crude Oil Sales — Third Party | Investments in Midstream Entities
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	0	0	0	0
Crude Oil Sales — Third Party | Corporate
Segment Reporting Information [Line Items]
Services and Sales Revenues - Third Party	$ 0	$ 0	$ 0	$ 0