Income Taxes - Income Tax Provision/(Benefit) and Deferred Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2011
Income Taxes [Line Items]
Undistributed Earnings of Foreign Subsidiaries	$ 39,000,000
Participation exemption rate established by the Tax Reform Act	10.00%
Deferred income tax assets benefits percentage	100.00%
Valuation allowance	$ 21,356,000	$ 17,823,000
Cash payments related to the deferred income tax liabilities associated with the 2004 Convertible Debt Securities	5,600,000	5,600,000	$ 6,000,000
Balance owed U.S. Tax Authorities related to deferred income tax liabilities associated with the 2004 Convertible Debt Securities repurchased	3,400,000
Domestic Country
Income Taxes [Line Items]
Valuation allowance	0
Operating loss carryforward	$ 39,000,000	45,000,000
Operating Loss Carryforwards, Expiration Dates	begin to expire in 2024 and can be utilized through 2030
Interest rate used for tax deduction			9.09%
State And Local Jurisdiction
Income Taxes [Line Items]
Valuation allowance	$ 2,400,000
Deferred income tax assets net of federal benefit	5,000,000
Operating loss carryforward	$ 50,000,000	63,000,000
Operating Loss Carryforwards, Expiration Dates	will expire beginning in 2018 and end in 2038
Foreign Country
Income Taxes [Line Items]
Valuation allowance	$ 18,900,000
Deferred income tax assets net of federal benefit	32,900,000
Operating loss carryforward	$ 103,000,000	$ 87,000,000
Operating Loss Carryforwards, Expiration Dates	2018