Additional Balance Sheet Detail and Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Other Accrued Liabilities		$ 3,971	$ 3,752
Accrued Income Taxes, Current		335	11,243
Accrual for Taxes Other than Income Taxes, Current		3,343	3,554
Interest Payable, Current		1,709	1,833
Operating Lease, Liability, Current		11,804	13,104
Accrued Salaries, Current		16,338	20,047
Silvertip acquisition contingent consideration		0	25,000
Deferred Revenue	[1]	16,472	16,672
Accrued liabilities and other		$ 68,457	$ 95,616

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