Fair Value Measurements and Marketable Securities - Summary of Marketable Securities (Detail) - USD ($)
$ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Amortized Cost |
$ 96,922
|
$ 149,691
|
| Gross Unrealized Gains |
|
4
|
| Gross Unrealized Losses |
(80)
|
(211)
|
| Fair Value |
96,842
|
149,484
|
| Corporate Bonds (Due within 1 Year) [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Amortized Cost |
68,777
|
112,828
|
| Gross Unrealized Gains |
|
1
|
| Gross Unrealized Losses |
(54)
|
(169)
|
| Fair Value |
68,723
|
112,660
|
| Corporate Bonds (Due After 1 Year Through 2 Years) [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Amortized Cost |
901
|
12,885
|
| Gross Unrealized Gains |
|
3
|
| Gross Unrealized Losses |
(2)
|
(32)
|
| Fair Value |
899
|
12,856
|
| Commercial Paper (Due within 1 Year) [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Amortized Cost |
27,244
|
19,478
|
| Gross Unrealized Losses |
(24)
|
(10)
|
| Fair Value |
$ 27,220
|
19,468
|
| U.S. Government Securities (Due within 1 Year) [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Amortized Cost |
|
4,500
|
| Fair Value |
|
$ 4,500
|