Distributions and Net Income Per Limited Partner Unit (Basic and Diluted Income Per Limited Partner Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 12,605	$ 9,164	$ 32,639	$ 26,603
(Distribution in excess of net income) net income in excess of distribution	780	(503)	485	3,486
Net income	$ 13,385	$ 8,661	$ 33,124	$ 30,089
Weighted average units outsanding:
Basic and diluted (shares)	27,172,230	27,059,730	27,097,642	27,059,730
Common units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 12,107	$ 4,819	$ 22,454	$ 14,057
(Distribution in excess of net income) net income in excess of distribution	780	(267)	624	1,852
Net income	$ 12,887	$ 4,552	$ 23,078	$ 15,909
Weighted average units outsanding:
Basic and diluted (shares)	27,172,230	14,373,615	18,686,701	14,373,615
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.47	$ 0.32	$ 1.23	$ 1.11
Subordinated units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 0	$ 4,254	$ 9,133	$ 12,407
(Distribution in excess of net income) net income in excess of distribution	0	(236)	(139)	1,634
Net income	$ 0	$ 4,018	$ 8,994	$ 14,041
Weighted average units outsanding:
Basic and diluted (shares)	0	12,686,115	8,410,941	12,686,115
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.00	$ 0.32	$ 1.07	$ 1.11
IDR Holders [Member]
Limited Partners' Capital Account [Line Items]
Subsequent distribution to IDR holders	$ 498	$ 91	$ 1,052	$ 139
(Distribution in excess of net income) net income in excess of distribution	0	0	0	0
Net income	$ 498	$ 91	$ 1,052	$ 139