Employee Benefit Plans - Other changes in the plan assets and benefit obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other changes recognized in accumulated other comprehensive income (loss)
Pension liability, beginning of year	$ 9,146	$ 8,450	$ 2,750
Plan change			1,276
Net prior service cost	(214)	(179)	(140)
Net loss	6,536	875	4,564
Pension liability, end of year	15,468	$ 9,146	$ 8,450
Amortization into next prior service cost over the next fiscal year	200
Amortization of actuarial loss over the next fiscal year	$ (700)