Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit pension plan, tax benefits	$ 700		$ 800
Total Members’ Capital
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unamortized defined benefit pension plan net actuarial losses	2,700		$ 2,700
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss included in noncontrolling interest	1,600	$ 1,600
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications from accumulated other comprehensive loss	$ 30	$ 44