Income Taxes Components of Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Corporate income taxes payable	$ 56	$ 32
Unrecognized tax benefits	8,250	7,777	$ 7,345
Interest accrued	824	680
Penalties	561	625
Income taxes payable	$ 9,691	$ 9,114

Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all domestic and foreign income tax obligations due. This amount is the total of current and noncurrent accrued income taxes.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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The amount of estimated interest accrued as of the balance sheet date arising from income tax examinations.

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The amount of estimated penalties accrued as of the balance sheet date arising from income tax examinations.

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Carrying value as of the balance sheet date of obligations incurred and payable for statutory income, sales, use, payroll, excise, real, property and other taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of unrecognized tax benefits.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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