Description of Business and Summary of Significant Accounting Policies (Accounts Receivable) (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Changes in the allowance for doubtful accounts | |||
| Allowance for Doubtful Accounts Receivable, Beginning Balance | $ 981 | $ 824 | $ 705 |
| Provision | 815 | 345 | 345 |
| Deductions | (649) | (188) | (226) |
| Allowance for Doubtful Accounts Receivable, Ending Balance | $ 1,147 | $ 981 | $ 824 |