Partners' Capital (Incentive Distribution Rights) (Details)	3 Months Ended
	Mar. 31, 2018 $ / shares
Minimum Quarterly Distribution [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.4375
Minimum Quarterly Distribution [Member] | Common Units [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	100.00%
Minimum Quarterly Distribution [Member] | Incentive Distribution Rights [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	0.00%
First Target Distribution [Member] | Common Units [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	100.00%
First Target Distribution [Member] | Incentive Distribution Rights [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	0.00%
First Target Distribution [Member] | Minimum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.4375
First Target Distribution [Member] | Maximum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.5031250
Second Target Distribution [Member] | Common Units [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	85.00%
Second Target Distribution [Member] | Incentive Distribution Rights [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	15.00%
Second Target Distribution [Member] | Minimum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.503125
Second Target Distribution [Member] | Maximum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.546875
Third Target Distribution [Member] | Common Units [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	75.00%
Third Target Distribution [Member] | Incentive Distribution Rights [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	25.00%
Third Target Distribution [Member] | Minimum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.546875
Third Target Distribution [Member] | Maximum [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	0.656250
Distributions Thereafter [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Total quarterly distribution per common unit target amount (in dollars per share)	$ 0.656250
Distributions Thereafter [Member] | Common Units [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	50.00%
Distributions Thereafter [Member] | Incentive Distribution Rights [Member]
Distribution Made To Managing Member Or General Partner [Line Items]
Marginal percentage interest in distributions	50.00%