Pension Plans and Other Postretirement Benefits - Domestic and Foreign Pension and Postretirement Defined Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Total net pension and postretirement benefits cost (credit)	$ 478	$ (903)	$ 1,055	$ (1,793)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,123	1,259	2,253	2,527
Interest cost	8,220	8,016	16,540	16,043
Expected return on assets	(9,445)	(10,760)	(18,897)	(21,524)
Amortization of prior service benefit	6	24	12	46
Total net pension and postretirement benefits cost (credit)	(96)	(1,461)	(92)	(2,908)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	30	49	59
Interest cost	549	542	1,098	1,084
Expected return on assets	0	(2)	0	(4)
Amortization of prior service benefit	0	(12)	0	(24)
Total net pension and postretirement benefits cost (credit)	$ 574	$ 558	$ 1,147	$ 1,115