Partners' Equity, Allocations and Cash Distribution - Distributions paid (Details) - USD ($) $ / shares in Units, $ in Thousands								3 Months Ended
	Jul. 31, 2020	Jul. 20, 2020	May 15, 2020	Apr. 27, 2020	Apr. 16, 2020	Feb. 18, 2020	Feb. 14, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
Cash Distribution Payment
Per Unit Cash Distribution (in dollars per unit)			$ 0.39375				$ 0.52500
Cash distribution, common units			$ 13,385				$ 17,848
Cash distribution, general partner			91				123
Cash distribution, incentive							320
Distributions, Total			$ 13,476				$ 18,291	$ 15,158	$ 19,973	$ 19,393	$ 18,997
Common Limited Partners
Distribution declared
Quarterly cash distributions declared (in dollars per unit)				$ 0.39375
Common Limited Partners | Subsequent event
Distribution declared
Quarterly cash distributions declared (in dollars per unit)	$ 0.45875
Common Limited Partners | Subsequent event | Annualized Basis [Member]
Distribution declared
Quarterly cash distributions declared (in dollars per unit)	$ 1.8350
Series A Preferred Limited Partners
Cash Distribution Payment
Per Unit Cash Distribution (in dollars per unit)			$ 0.609375			$ 0.609375
Distribution declared
Quarterly cash distributions declared (in dollars per unit)					$ 0.609375
Series A Preferred Limited Partners | Subsequent event
Distribution declared
Quarterly cash distributions declared (in dollars per unit)		$ 0.609375
Series A Preferred Limited Partners | Subsequent event | Annualized Basis [Member]
Distribution declared
Quarterly cash distributions declared (in dollars per unit)		$ 2.4375
Limited Partner Interest | Common Limited Partners
Cash Distribution Payment
Distributions, Total								13,385	17,848	17,338	16,998
Limited Partner Interest | Series A Preferred Limited Partners
Cash Distribution Payment
Distributions, Total								1,682	1,682	1,682	1,682
General Partner, Global GP LLC
Cash Distribution Payment
Distributions, Total								$ 91	$ 443	$ 373	$ 317