Additional Balance Sheet Detail and Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Other Accrued Liabilities	$ 7,084	$ 10,524
Accrued Income Taxes, Current	585	16,474
Accrual for Taxes Other than Income Taxes, Current	3,617	3,639
Interest Payable, Current	1,324	1,589
Operating Lease, Liability, Current	13,207	0
Accrued Salaries, Current	14,119	22,229
Silvertip acquisition contingent consideration	49,635	25,000
Deferred Revenue	26,616	3,164
Accrued liabilities and other	$ 116,187	$ 82,619