Pension - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 191	$ 359	$ 572	$ 1,100
Interest cost	259	308	778	944
Expected return on plan assets	(231)	(266)	(692)	(815)
Amortization of prior service cost	(25)	(19)	(75)	(58)
Amortization of actuarial loss	15	84	44	252
Net periodic pension cost	$ 209	$ 466	$ 627	$ 1,423