Long-Term Incentive Plan - Unit-based (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Long-Term Incentive Plan
Number of common units initially authorized for issuance under LTIP (in shares)	4,300,000
Number of common units available for issuance	3,016,234
Number of Non-vested Units
Outstanding non-vested units at the beginning of the period (in shares)	730,141	912,564
Vested (in shares)	(148,842)	(153,966)
Forfeited (in shares)	(18,393)	(28,457)
Outstanding non-vested units at the end of the period (in shares)	562,906	730,141	912,564
Weighted Average Grant Date Fair Value
Outstanding non-vested units at the beginning of the period (in dollars per share)	$ 13.57	$ 15.99
Vested (in dollars per share)	27.41	27.93
Forfeited (in dollars per share)	18.66	13.40
Outstanding non-vested units at the end of the period (in dollars per share)	$ 9.74	$ 13.57	$ 15.99
Unrecognized compensation cost related to the non-vested awards	$ 2,700,000
Repurchase Program
Aggregate common units authorized to be acquired (in shares)	1,242,427
Common units repurchased by General Partner (in shares)	0
Common units repurchased to date (in shares)	838,505
Common units repurchased to date, value	$ 24,800,000
Performance costs paid	300,000	$ 400,000
Phantom Unit Awards [Member]
Weighted Average Grant Date Fair Value
Compensation expenses	$ 2,000,000	$ 3,100,000	$ 3,900,000
CEO Authorized LTIP
Long-Term Incentive Plan
Number of years for which Plan was approved			3 years
Aggregate amount of CEO authorized shares to grant in each calendar year			$ 2,000,000
Maximum value of grant			$ 550,000
CEO Authorized LTIP expiration period			6 years