Accrued Liabilities - Carrying Value of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued Liabilities and Other Liabilities [Abstract]
Wages, severance and related taxes	$ 65,892	$ 58,953
Current deferred revenue	53,371	54,255
Accrued rebates	32,192	37,170
Accrued interest	20,610	18,781
Employee benefits	27,707	17,791
Lease liabilities	14,840	14,072
Other (individual items less than 5% of total current liabilities)	62,029	82,777
Accrued liabilities	$ 276,641	$ 283,799