Equity-Based Compensation Plans (Summary of Service-Based and Performance-Based Awards) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Service-Based Awards
Number of Phantom Units
Unvested at December 31, 2019 (in units) | shares	148,077
Granted (in units) | shares	107,572
Forfeited (in units) | shares	(244)
Settled (in units) | shares	(89,743)
Unvested at December 31, 2020 (in units) | shares	165,662
Average Grant Date Fair Value
Unvested at December 31, 2019 (in dollars unit) | $ / shares	$ 27.85
Granted (in dollars per unit) | $ / shares	5.86
Forfeited (in dollars per unit) | $ / shares	32.43
Settled (in dollars per unit) | $ / shares	32.24
Unvested at December 31, 2020 (in dollars per unit) | $ / shares	$ 11.19
Total Value (in thousands)
Unvested at December 31, 2019 | $	$ 4,124
Granted | $	630
Forfeited | $	(8)
Settled | $	(2,893)
Unvested at December 31, 2020 | $	$ 1,853
Performance-Based Awards
Number of Phantom Units
Unvested at December 31, 2019 (in units) | shares	162,771
Granted (in units) | shares	0
Forfeited (in units) | shares	(367)
Settled (in units) | shares	(162,404)
Unvested at December 31, 2020 (in units) | shares	0
Average Grant Date Fair Value
Unvested at December 31, 2019 (in dollars unit) | $ / shares	$ 32.02
Granted (in dollars per unit) | $ / shares	0
Forfeited (in dollars per unit) | $ / shares	32.43
Settled (in dollars per unit) | $ / shares	32.03
Unvested at December 31, 2020 (in dollars per unit) | $ / shares	$ 0
Total Value (in thousands)
Unvested at December 31, 2019 | $	$ 5,214
Granted | $	0
Forfeited | $	(12)
Settled | $	(5,202)
Unvested at December 31, 2020 | $	$ 0