Earnings Per Unit (Schedule Of Basic And Diluted Earnings Per Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Unit [Line Items]
Distributions declared									$ 59,124	$ 54,022	$ 26,032
Earnings in excess of (less than) distributions									(257)	2,783
Earnings less than distributions											(3,023)
Net income attributable to the partnership					$ 16,442	$ 14,199	$ 13,982	$ 12,182	58,867	56,805	23,009	[1]
Limited Partners [Member]
Earnings Per Unit [Line Items]
Distributions declared									57,893	52,941	25,511
General Partner [Member]
Earnings Per Unit [Line Items]
Distributions declared									1,231	1,081	521
Earnings in excess of (less than) distributions									(54)	55
Earnings less than distributions											(61)
Net income attributable to the partnership									1,177	1,136	460
Common Units [Member]
Earnings Per Unit [Line Items]
Earnings per limited partner unit (basic and diluted)	$ 0.50	$ 0.45	$ 0.40	$ 0.46	$ 0.50	$ 0.44	$ 0.43	$ 0.38
Common Units [Member] | Limited Partners [Member]
Earnings Per Unit [Line Items]
Distributions declared									28,974	26,485	12,760
Earnings in excess of (less than) distributions									(105)	1,363
Earnings less than distributions											(1,482)
Net income attributable to the partnership									$ 28,869	$ 27,848	$ 11,278
Weighted average limited partner units outstanding (basic and diluted)									15,916,000	15,904,000	15,897,000	[1]
Earnings per limited partner unit (basic and diluted)									$ 1.81	$ 1.75	$ 0.71	[1]
Subordinated Units [Member]
Earnings Per Unit [Line Items]
Earnings per limited partner unit (basic and diluted)	$ 0.50	$ 0.45	$ 0.40	$ 0.46	$ 0.50	$ 0.44	$ 0.43	$ 0.38
Subordinated Units [Member] | Limited Partners [Member]
Earnings Per Unit [Line Items]
Distributions declared									$ 28,919	$ 26,456	$ 12,751
Earnings in excess of (less than) distributions									(98)	1,365
Earnings less than distributions											(1,480)
Net income attributable to the partnership									$ 28,821	$ 27,821	$ 11,271
Weighted average limited partner units outstanding (basic and diluted)									15,890,000	15,890,000	15,890,000	[1]
Earnings per limited partner unit (basic and diluted)									$ 1.81	$ 1.75	$ 0.71	[1]

[1] Recast to include historical results of operations related to net assets acquired in a transfer between entities under common control. See Notes 1 and 4 in the accompanying notes to consolidated financial statements for further discussion.