Held-to-Maturity-Investments - Amortized Cost and Fair Value of Held-to-Maturity Investments (Detail) - USD ($) $ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Investments, Debt and Equity Securities [Abstract] | ||
| Held-to-Maturity securities, Maturing in one year or less, Amortized Cost | $ 38,551 | $ 70,055 |
| Held to Maturity, Amortized Cost, Total | 38,551 | 72,556 |
| Held-to-Maturity securities, Maturing in one year or less, Fair Value | 38,504 | |
| Held-to-Maturity, Fair Value, Total | $ 38,504 | $ 72,532 |