Long-Term Debt Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Feb. 16, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total carrying value of debt	$ 114,489		$ 267
Other debt	721		191
Less: current maturities	(107)		(111)
Long-term debt, less current portion	114,382		156
Senior Notes
Debt Instrument [Line Items]
Less: debt discount and issuance costs, net	(29,487)		0
Total carrying value of debt	114,263		0
Equity component of exchangeable notes, net of issuance costs	(26,699)		0
Loans Payable
Debt Instrument [Line Items]
Other debt	$ 226		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

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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