Patents Cost and Accumulated Amortization (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Patents [Line Items] | |||
| Patent cost, disposals | $ 0 | $ 500 | $ 3,000 |
| Accumulated amortization, disposals | 0 | 120 | 298 |
| Proceeds from Sale of Intangible Assets | $ 0 | $ 750 | $ 3,500 |