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Distributions and Net Income Per Limited Partner Unit (Distributions Declared) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		$ 12,295	$ 9,764
Distributions declared		13,547	9,834
Distribution in excess of net income		(1,252)	(70)
IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		733	231
Distributions declared with respect to the incentive distribution rights		733	231
Distribution in excess of net income		0	0
Common units [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		11,562	5,064
Distributions declared		12,814	5,101
Distribution in excess of net income		(1,252)	(37)
Subordinated units [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership			4,469
Distributions declared			4,502
Distribution in excess of net income			(33)
Cash Distribution [Member] \| IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Distributions declared with respect to the incentive distribution rights		$ 733	231
Cash Distribution [Member] \| IDR Holders [Member] \| Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared and paid to IDR holders	$ 733
Cash Distribution [Member] \| Common units [Member]
Distribution Made to Limited Partner [Line Items]
Minimum quarterly distribution per unit (in usd per unit)		$ 0.2750
Distributions declared		$ 12,814	5,101
Cash Distribution [Member] \| Subordinated units [Member]
Distribution Made to Limited Partner [Line Items]
Distributions declared		$ 0	$ 4,502
Cash Distribution [Member] \| Common And Subordinated Units [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)		$ 0.3163
Cash Distribution [Member] \| Common And Subordinated Units [Member] \| Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared per unit (in usd per unit)	$ 0.3975
Above $0.3163 up to $0.3438 \| Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)		0.3163
Above $0.3163 up to $0.3438 \| Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)		$ 0.3438
Above $0.3163 up to $0.3438 \| IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		15.00%
Above $0.3163 up to $0.3438 \| Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		85.00%
Above $0.3438 up to $0.4125 \| Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)		$ 0.3438
Above $0.3438 up to $0.4125 \| Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Quarterly incentive distribution, per unit, distribution threshold		$ 0.4125
Above $0.3438 up to $0.4125 \| IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		25.00%
Above $0.3438 up to $0.4125 \| Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		75.00%
Above $0.4125 \| Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Quarterly incentive distribution, per unit, distribution threshold		$ 0.4125
Above $0.4125 \| IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		50.00%
Above $0.4125 \| Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions		50.00%