Other Income, Net (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
| Other Income and Expenses [Abstract] | ||||
| Interest income | $ 296 | $ 400 | $ 488 | $ 579 |
| Other Nonoperating Income | 1 | 0 | 0 | 16 |
| Insurance policy expense | (12) | (32) | (36) | (32) |
| Other nonoperating expense | 0 | (231) | 0 | 0 |
| Other income, net | $ 285 | $ 137 | $ 452 | $ 563 |