Additional Balance Sheet Detail and Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Other Accrued Liabilities		$ 4,163	$ 10,524
Accrued Income Taxes, Current		11,243	16,474
Accrual for Taxes Other than Income Taxes, Current		3,554	3,639
Interest Payable, Current		1,833	1,589
Operating Lease, Liability, Current		13,104	0
Accrued Salaries, Current		20,047	22,229
Silvertip acquisition contingent consideration		25,000	25,000
Deferred Revenue	[1]	16,672	3,164
Accrued liabilities and other		$ 95,616	$ 82,619

[1] ⁽¹⁾ See Note 21 -- Commitments and Contingencies for additional details on deferred revenue liabilities