Marketable Securities - Summary of Marketable Securities Classified as Available-for-Sale (Details) - USD ($)
$ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
|
$ 84,434
|
| Unrealized Gains |
|
1
|
| Unrealized Losses |
|
(105)
|
| Fair Value |
|
84,330
|
| Short-Term Marketable Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
$ 71,419
|
79,307
|
| Unrealized Losses |
(138)
|
(95)
|
| Fair Value |
71,281
|
79,212
|
| Short-Term Marketable Securities | Commercial Paper |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
5,445
|
6,369
|
| Unrealized Losses |
(17)
|
(10)
|
| Fair Value |
5,428
|
6,359
|
| Short-Term Marketable Securities | Corporate Debt Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
10,167
|
16,162
|
| Unrealized Losses |
(27)
|
(13)
|
| Fair Value |
10,140
|
16,149
|
| Short-Term Marketable Securities | Asset-backed Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
14,446
|
14,604
|
| Unrealized Losses |
(42)
|
(16)
|
| Fair Value |
14,404
|
14,588
|
| Short-Term Marketable Securities | US Government Debt Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
41,361
|
42,172
|
| Unrealized Losses |
(52)
|
(56)
|
| Fair Value |
$ 41,309
|
42,116
|
| Long-Term Marketable Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
|
5,127
|
| Unrealized Gains |
|
1
|
| Unrealized Losses |
|
(10)
|
| Fair Value |
|
5,118
|
| Long-Term Marketable Securities | Asset-backed Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
|
2,752
|
| Unrealized Losses |
|
(10)
|
| Fair Value |
|
2,742
|
| Long-Term Marketable Securities | US Government Debt Securities |
|
|
| Schedule Of Available For Sale Securities [Line Items] |
|
|
| Amortized Cost Basis |
|
2,375
|
| Unrealized Gains |
|
1
|
| Fair Value |
|
$ 2,376
|