Employee Benefits - Components of Net Periodic Pension Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 3,659	$ 3,145	$ 2,820
Interest cost	851	840	765
Expected return on plan assets	(517)	(475)	(360)
Recognition of actuarial loss	237	340	350
Total defined benefit pension expense	$ 4,230	$ 3,850	$ 3,575