Equity-Based Awards (Details) - USD ($)			1 Months Ended		3 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Feb. 28, 2018	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Weighted Average Grant Date Fair Value per Unit
General and administrative expenses					$ 6,804,000	$ 8,763,000
Distribution Equivalent Rights | Related party accrued liabilities
Weighted Average Grant Date Fair Value per Unit
Distributions paid related to DERs					$ 500,000
LTIP
Weighted Average Grant Date Fair Value per Unit
Additional expense from change in fair value of unit awards	$ 100,000
LTIP | General Partner
Weighted Average Grant Date Fair Value per Unit
Cash payments for tax-withholding requirements on unit awards	$ 1,700,000
Units issued by the Company	81,708
Grant date fair value	$ 28.65
LTIP | Performance Based Phantom units
Number of Units
Vested (in units)		(139,810)
LTIP | Performance Based Phantom units | General Partner
Weighted Average Grant Date Fair Value per Unit
Cash distributions paid				$ 2,300,000
Affiliate Grants
Number of Units
Nonvested at the beginning of the period (in units)				706,970	706,970
Granted (in units)					359,843
Forfeitures (in units)					(16,123)
Nonvested at the end of the period (in units)		706,970			1,050,690
Weighted Average Grant Date Fair Value per Unit
Nonvested at the beginning of the period (in dollars per unit)				$ 22.82	$ 22.82
Granted (in dollars per unit)					28.65
Forfeitures (in dollar per unit)					23.76
Nonvested at the end of the period (in dollars per unit)		$ 22.82			$ 24.80
Affiliate Grants | Phantom units
Number of Units
Nonvested at the beginning of the period (in units)				595,866	595,866
Granted (in units)					243,442
Forfeitures (in units)					(16,123)
Nonvested at the end of the period (in units)		595,866			823,185
Weighted Average Grant Date Fair Value per Unit
Nonvested at the beginning of the period (in dollars per unit)				$ 22.32	$ 22.32
Granted (in dollars per unit)					28.65
Forfeitures (in dollar per unit)					23.76
Nonvested at the end of the period (in dollars per unit)		$ 22.32			$ 24.16
Affiliate Grants | Performance Based Phantom units
Number of Units
Nonvested at the beginning of the period (in units)				111,104	111,104
Granted (in units)					116,401
Nonvested at the end of the period (in units)		111,104			227,505
Weighted Average Grant Date Fair Value per Unit
Nonvested at the beginning of the period (in dollars per unit)				$ 25.52	$ 25.52
Granted (in dollars per unit)					28.65
Nonvested at the end of the period (in dollars per unit)		$ 25.52			$ 27.12
Unpaid DER amounts		$ 900,000			$ 1,100,000
Affiliate Grants | Performance Based Phantom units | Accrued liabilities
Weighted Average Grant Date Fair Value per Unit
Unpaid DER amounts		$ 700,000			700,000
Affiliate Grants | Performance Based Phantom units | Other long-term liabilities
Weighted Average Grant Date Fair Value per Unit
Unpaid DER amounts					$ 400,000	$ 200,000
Affiliate Grants | Distribution Equivalent Rights
Weighted Average Grant Date Fair Value per Unit
Period in which distribution related to DERs are required to be paid					60 days
Director Grants
Number of Units
Nonvested at the beginning of the period (in units)				15,840	15,840
Granted (in units)					13,964
Vested (in units)					(15,840)
Nonvested at the end of the period (in units)		15,840			13,964
Weighted Average Grant Date Fair Value per Unit
Nonvested at the beginning of the period (in dollars per unit)				$ 25.25	$ 25.25
Granted (in dollars per unit)					28.65
Vested (in dollars per unit)					25.25
Nonvested at the end of the period (in dollars per unit)		$ 25.25			$ 28.65
Director Grants | Phantom units
Number of Units
Nonvested at the beginning of the period (in units)				15,840	15,840
Granted (in units)					13,964
Vested (in units)					(15,840)
Nonvested at the end of the period (in units)		15,840			13,964
Weighted Average Grant Date Fair Value per Unit
Nonvested at the beginning of the period (in dollars per unit)				$ 25.25	$ 25.25
Granted (in dollars per unit)					28.65
Vested (in dollars per unit)					25.25
Nonvested at the end of the period (in dollars per unit)		$ 25.25			$ 28.65
Fair value of units granted			$ 400,000
Director Grants | Distribution Equivalent Rights
Weighted Average Grant Date Fair Value per Unit
Period in which distribution related to DERs are required to be paid					60 days