Earnings Per Share - Computation of Basic and Diluted Net Earnings (Loss) Per Share (Details) - USD ($) shares in Thousands, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Numerator: | |||||||||||
| Net income | $ 28,488 | $ 13,964 | $ 10,933 | $ 13,632 | $ 11,402 | $ 5,999 | $ 7,839 | $ 8,599 | $ 67,017 | $ 33,839 | $ 47,605 |
| Denominator: | |||||||||||
| Denominator for basic earnings per share – weighted average shares | 20,767 | 20,704 | 20,713 | ||||||||
| Effect of dilutive securities: | |||||||||||
| Employee stock options (in shares) | 80 | 69 | 74 | ||||||||
| Denominator for diluted earnings per share – weighted average shares | 20,847 | 20,773 | 20,787 | ||||||||