Long-Term Debt Schedule of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Feb. 16, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total carrying value of debt	$ 113,146		$ 267
Other	740		191
Less: current maturities	(108)		(111)
Long-term debt, less current portion	113,038		156
Senior Notes
Debt Instrument [Line Items]
Less: debt discount and issuance costs, net	30,869		0
Total carrying value of debt	112,881		0
Equity component of exchangeable notes, net of issuance costs	26,699		0
Loans Payable
Debt Instrument [Line Items]
Other	$ 265		267
4.50% Exchangeable Senior Notes Due 2023
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	4.50%	4.50%
4.50% Exchangeable Senior Notes Due 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 143,750		$ 0