Long-Term Incentive Plan Units Long-Term Incentive Plan Units (Unvested LTIP Units) (Details) - Long-Term Incentive Plan Units [Member] - shares		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)		37,709	39,432
Director [Member]
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)		14,440	14,440
Grant Date		Sep. 12, 2018	Sep. 12, 2018
Vesting Date(1)	[1]	Sep. 11, 2019	Sep. 11, 2019
Vest December 11, 2019 [Member] | Dedicated or partially dedicated personnel [Member]
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)		8,692	8,692
Grant Date		Dec. 11, 2018	Dec. 11, 2018
Vesting Date(1)	[1]	Dec. 11, 2019	Dec. 11, 2019
Vest December 11, 2020 [Member] | Dedicated or partially dedicated personnel [Member]
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)		8,691	8,691
Grant Date		Dec. 11, 2018	Dec. 11, 2018
Vesting Date(1)	[1]	Dec. 11, 2020	Dec. 11, 2020
Vest March 7, 2019 [Member] | Dedicated or partially dedicated personnel [Member]
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)			1,723
Grant Date			Mar. 07, 2018
Vesting Date(1)	[1]		Mar. 07, 2019
Vest December 12, 2019 [Member] | Dedicated or partially dedicated personnel [Member]
Schedule of Unvested LTIP Units [Line Items]
Number of OP LTIP Units (in units)		5,886	5,886
Grant Date		Dec. 12, 2017	Dec. 12, 2017
Vesting Date(1)	[1]	Dec. 12, 2019	Dec. 12, 2019

[1] Date at which such OP LTIP Units will vest and become non-forfeitable.