Pension Plans and Other Postretirement Benefits - Contributions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Minimum funding requirement	$ 0
Expected contributions (approximations)	0
Supplemental Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Expected contributions (approximations)	$ 1,307