Employee Benefit Plans - Benefit Obligations of Defined Benefit Plan (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Sep. 12, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year				$ 1,187	$ 1,023
Service cost		$ 953	$ 35	1,159	86
Interest cost		16	11	47	32
Benefit obligation, end of year		$ 2,393	$ 1,141	$ 2,393	$ 1,141
Defined benefit plan, prior period expense	$ 850