Partners' Capital and Distributions - Percentage of Incentive Distribution Rights to Partnership's Unitholders and General Partner (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2017 $ / shares
Minimum [Member] | Above $0.3875 up to $0.4456 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	$ 0.3875
Minimum [Member] | Above $0.4456 up to $0.4844 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	0.4456
Minimum [Member] | Above $0.4844 up to $0.5813 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	0.4844
Minimum [Member] | Above $0.5813 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	0.5813
Maximum [Member] | Above $0.3875 up to $0.4456 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	0.4456
Maximum [Member] | Above $0.4456 up to $0.4844 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	0.4844
Maximum [Member] | Above $0.4844 up to $0.5813 [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Cash distribution paid, per unit	$ 0.5813