Employee Benefit Plans - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	$ (1,743)	$ (583)	$ 3,119
Amortization of losses (gains)	673	466	2,526
Amortization of prior service cost	0	0	0
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	149	(89)	(99)
Amortization of losses (gains)	2	(1)	(13)
Amortization of prior service cost	$ 0	$ 0	$ 0