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
	Mar. 31, 2018	Mar. 31, 2017
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 13,547	$ 9,834
Distribution in excess of net income	(1,252)	(70)
Net income	$ 12,295	$ 9,764
Weighted average units outsanding:
Basic and diluted (shares)	32,236,449	27,059,730
Common units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 12,814	$ 5,101
Distribution in excess of net income	(1,252)	(37)
Net income	$ 11,562	$ 5,064
Weighted average units outsanding:
Basic and diluted (shares)	32,236,449	14,373,615
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.36	$ 0.35
Subordinated units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared		$ 4,502
Distribution in excess of net income		(33)
Net income		$ 4,469
Weighted average units outsanding:
Basic and diluted (shares)		12,686,115
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.00	$ 0.35
IDR Holders [Member]
Limited Partners' Capital Account [Line Items]
Subsequent distribution to IDR holders	$ 733	$ 231
Distribution in excess of net income	0	0
Net income	$ 733	$ 231