Partners' Capital and Distributions - Percentage of Incentive Distribution Rights to Partnership's Unitholders and General Partner (Detail)	9 Months Ended
	Sep. 30, 2017
Above $0.3875 up to $0.4456 [Member] | Unitholders [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	100.00%
Above $0.3875 up to $0.4456 [Member] | General Partners [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	0.00%
Above $0.4456 up to $0.4844 [Member] | Unitholders [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	85.00%
Above $0.4456 up to $0.4844 [Member] | General Partners [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	15.00%
Above $0.4844 up to $0.5813 [Member] | Unitholders [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	75.00%
Above $0.4844 up to $0.5813 [Member] | General Partners [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	25.00%
Above $0.5813 [Member] | Unitholders [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	50.00%
Above $0.5813 [Member] | General Partners [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Marginal Percentage Interest in Distributions	50.00%