Employee Benefit Plans - Projected Benefit Obligation and Accumulated Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Plan assets in excess of projected benefit obligation:
Projected benefit obligation	$ 6,577	$ 4,745
Fair value of plan assets	6,615	5,313	$ 5,356
Plan assets in excess of accumulated benefit obligation:
Accumulated benefit obligation	5,056	4,173
Fair value of plan assets	$ 6,615	$ 5,313