Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 25, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 72,177	$ 71,467	$ 66,558	$ 61,421	$ 56,883		$ 47,381	$ 40,312	$ 37,640		$ 271,623	$ 182,216	$ 120,852
Operating income	40,294	39,013	37,668	31,791	33,363		25,135	23,102	20,763		148,766	102,363	70,940
Income before income taxes	38,560	38,835	37,485	31,529	33,365		22,407	20,089	19,544		146,409	95,405	64,985
Net income	38,560	38,835	37,485	31,529	33,365	$ 34,970	14,509	$ 12,424	$ 12,249	$ 37,577	146,409	72,547	$ 40,128
Net income attributable to Oasis Midstream Partners LP	$ 15,281	$ 12,376	$ 12,444	$ 9,954	$ 11,112	11,638	$ 526				50,055	11,638
Common Units
Condensed Financial Statements, Captions [Line Items]
Basic and Diluted (in usd per share)	$ 0.54	$ 0.45	$ 0.45	$ 0.36	$ 0.41		$ 0.02
Limited Partners
Condensed Financial Statements, Captions [Line Items]
Net income						0
Net income attributable to Oasis Midstream Partners LP						$ 11,638					49,943
Limited Partners | Common Units
Condensed Financial Statements, Captions [Line Items]
Net income											25,913
Net income attributable to Oasis Midstream Partners LP											$ 26,416	5,819
Basic and Diluted (in usd per share)						$ 0.43					$ 1.82
Limited Partners | Subordinated Units
Condensed Financial Statements, Captions [Line Items]
Net income						$ 5,819					$ 24,030
Net income attributable to Oasis Midstream Partners LP											$ 23,527	$ 5,819