Income Taxes - Principal Components of the Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred income tax assets:
Accruals not yet tax deductible	$ 152,288	$ 133,349
Stock compensation	12,995	11,616
Net operating loss and research & development tax credit carryforwards	68,809	63,517
Amortization of research and experimental costs	78,169	43,034
Other	66,749	55,800
Deferred tax assets gross	379,010	307,316
Valuation allowance	(48,516)	(40,878)
Deferred tax assets net	330,494	266,438
Deferred income tax liabilities:
Depreciation, tax in excess of book	(57,641)	(49,889)
Pension and postretirement healthcare plan obligations	(82,682)	(58,843)
Withholding tax	(29,904)	(23,632)
Other	(32,597)	(28,561)
Deferred tax liabilities net	(202,824)	(160,925)
Total	$ 127,670	$ 105,513