Investments - Proceeds from Available-for-Sale Securities (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Available-for-sale securities, proceeds and realized gains (losses) included in earnings | |||
| Proceeds from sales | $ 3,062 | $ 6,303 | $ 15,065 |
| Gross realized gains | 416 | 404 | 929 |
| Gross realized losses | $ 27 | $ 106 | $ 264 |
| Other information | |||
| Average period of time for which securities were traded continuously at a price below book value for securities sold at a loss | 9 months | ||