Additional Balance Sheet Detail and Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Other Accrued Liabilities		$ 2,991	$ 3,752
Unrealized Gain (Loss) on Derivatives		34,224	411
Accrued Income Taxes, Current		14,784	11,243
Accrual for Taxes Other than Income Taxes, Current		3,392	3,554
Interest Payable, Current		5,218	1,833
Operating Lease, Liability, Current		12,716	13,104
Accrued Salaries, Current		23,202	20,047
Silvertip acquisition contingent consideration		0	25,000
Deferred Revenue	[1]	11,463	16,672
Accrued liabilities and other		$ 107,990	$ 95,616

[1] (1) See Note 17 -- Commitments and Contingencies for additional details on deferred revenue liabilities