Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total Midstream Services—Affiliate	$ 47,167	$ 22,670	$ 112,259	$ 51,734
Investment Income	1,070	1,060	3,509	3,418
Total Revenues	48,237	23,730	115,768	55,152
Income (Loss) Before Income Taxes	33,472	17,186	78,599	33,898
Total Assets	340,866		340,866		$ 305,318
Gathering Systems
Segment Reporting Information [Line Items]
Total Midstream Services—Affiliate	25,887	14,999	72,291	37,598
Investment Income	0	0	0	0
Total Revenues	25,887	14,999	72,291	37,598
Income (Loss) Before Income Taxes	19,280	10,933	56,390	25,284
Total Assets	208,028		208,028		201,744
Fresh Water Delivery
Segment Reporting Information [Line Items]
Total Midstream Services—Affiliate	21,280	7,671	39,968	14,136
Investment Income	0	0	0	0
Total Revenues	21,280	7,671	39,968	14,136
Income (Loss) Before Income Taxes	18,186	6,490	29,272	10,730
Total Assets	53,813		53,813		49,189
Investments in White Cliffs and Other
Segment Reporting Information [Line Items]
Total Midstream Services—Affiliate	0	0	0	0
Investment Income	1,070	1,060	3,509	3,418
Total Revenues	1,070	1,060	3,509	3,418
Income (Loss) Before Income Taxes	(3,994)	$ (237)	(7,063)	$ (2,116)
Total Assets	$ 79,025		$ 79,025		$ 54,385