|
Fair Value Measurements and Marketable Securities - Summary of Company's Available-for-Sale Securities (Detail) (USD $)
In Thousands, unless otherwise specified |
Mar. 31, 2013
|
Dec. 31, 2012
|
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | $ 83,878 | $ 59,808 |
| Unrealized Gain | 18 | 18 |
| Unrealized Loss | (13) | (7) |
| Fair Value | 83,883 | 59,819 |
|
Money market funds [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 9,345 | 5,886 |
| Fair Value | 9,345 | 5,886 |
|
Certificates of deposit [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 2,125 | 1,185 |
| Fair Value | 2,125 | 1,185 |
|
Corporate debt securities [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 42,982 | 20,237 |
| Unrealized Gain | 8 | 6 |
| Unrealized Loss | (12) | (1) |
| Fair Value | 42,978 | 20,242 |
|
Government securities [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 35,654 | 27,893 |
| Unrealized Gain | 11 | 12 |
| Unrealized Loss | (1) | (6) |
| Fair Value | 35,664 | 27,899 |
|
Commercial paper [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 13,990 | 15,613 |
| Fair Value | 13,990 | 15,613 |
|
Marketable securities including cash equivalents [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 104,096 | 70,814 |
| Unrealized Gain | 19 | 18 |
| Unrealized Loss | (13) | (7) |
| Fair Value | 104,102 | 70,825 |
|
Less cash equivalents [Member]
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | (20,218) | (11,006) |
| Unrealized Gain | (1) | |
| Fair Value | $ (20,219) | $ (11,006) |