Held-to-Maturity Investments - Schedule of Held-to-Maturity Investments (Detail) - USD ($)
$ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Schedule of Held-to-maturity Securities [Line Items] |
|
|
| Held-to-maturity investments, Amortized Cost |
$ 38,551
|
$ 72,556
|
| Held-to-maturity investments, Gross Unrealized Gains |
|
2
|
| Held-to-maturity investments, Gross Unrealized Losses |
(47)
|
(26)
|
| Held-to-maturity investments, Fair Value, Total |
38,504
|
72,532
|
| US Treasury Securities [Member] |
|
|
| Schedule of Held-to-maturity Securities [Line Items] |
|
|
| Held-to-maturity investments, Amortized Cost |
38,551
|
|
| Held-to-maturity investments, Gross Unrealized Losses |
(47)
|
|
| Held-to-maturity investments, Fair Value, Total |
$ 38,504
|
|
| U.S. Government Treasury and Agency Securities [Member] |
|
|
| Schedule of Held-to-maturity Securities [Line Items] |
|
|
| Held-to-maturity investments, Amortized Cost |
|
72,556
|
| Held-to-maturity investments, Gross Unrealized Gains |
|
2
|
| Held-to-maturity investments, Gross Unrealized Losses |
|
(26)
|
| Held-to-maturity investments, Fair Value, Total |
|
$ 72,532
|