Additional Balance Sheet Detail and Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Other Accrued Liabilities		$ 6,750	$ 10,524
Accrued Income Taxes, Current		7,518	16,474
Accrual for Taxes Other than Income Taxes, Current		3,657	3,639
Interest Payable, Current		4,623	1,589
Operating Lease, Liability, Current		13,199	0
Accrued Salaries, Current		19,554	22,229
Silvertip acquisition contingent consideration		49,817	25,000
Deferred Revenue	[1]	12,488	3,164
Accrued liabilities and other		$ 117,606	$ 82,619

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