Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 46	$ 0	$ 0
Interest cost	2,595	2,058	2,139
Expected return on plan assets	(3,339)	(2,376)	(2,419)
Amortization of actuarial net loss	1,024	1,092	933
Total net periodic benefit cost	$ 326	$ 774	$ 653