Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Fair Value Measurement (Schedule of Reconciliation of Fair Value Measurements of Assets and Liabilities Utilizing Level 3 Inputs) (Details))

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Fair Value Measurement (Schedule of Reconciliation of Fair Value Measurements of Assets and Liabilities Utilizing Level 3 Inputs) (Details)) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Reconciliation of Fair Value Measurements of Assets and Liabilities Utilizing Level 3 Inputs [Roll Forward]    
Fair value as of January 1 $ 2,619 $ 6,991
Settlements (3,997) (3,500)
Change in fair value recognized in earnings 1,378 (872)
Fair value as of December 31 $ 2,619