Employee Benefit Plans - Components of Net Periodic Pension/Postretirement Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Settlement expense		$ 19,900
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year			$ 2
Interest cost on projected benefit obligations		305	1,228
Expected return on plan assets		(835)	(1,596)
Amortization of net loss		262	525
Settlement expense		19,900	641
Net periodic pension/postretirement benefit cost		19,632	800
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 103	124	121
Interest cost on projected benefit obligations	210	189	195
Amortization of actuarial gain	(117)	(30)	(49)
Amortization of prior service credit		(13)	(25)
Net periodic pension/postretirement benefit cost	$ 196	$ 270	$ 242