Realized and Net Change in Unrealized Gains (Losses) on Investments (Detail) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
|
| Gain (Loss) on Investments [Line Items] | ||||
| Realized Gains (Losses) on other investments | $ 1,282 | $ (460) | $ 1,274 | $ 5,152 |
| Net Change in Unrealized Gains (Losses) on other investments | (2,779) | 239 | (3,233) | (6,252) |
| Total realized and net change in unrealized gains (losses) on other investments | $ (1,497) | $ (221) | $ (1,959) | $ (1,100) |