|
Fair Value Measurements and Marketable Securities - Financial Assets at Fair Value on Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified
|
Sep. 30, 2012
|
Dec. 31, 2011
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
$ 65,825
|
$ 20,258
|
|
Money Market Funds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
3,861
|
4,050
|
|
Certificate Of Deposits [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
485
|
|
|
Corporate Bonds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
20,160
|
4,690
|
|
U.S. Government Securities [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
29,004
|
5,970
|
|
Commercial Paper [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
12,315
|
5,548
|
|
Basis of Fair Value Measurements Level 1 [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
3,861
|
4,050
|
|
Basis of Fair Value Measurements Level 1 [Member] | Money Market Funds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
3,861
|
4,050
|
|
Basis of Fair Value Measurements Level 1 [Member] | Certificate Of Deposits [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 1 [Member] | Corporate Bonds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 1 [Member] | U.S. Government Securities [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 1 [Member] | Commercial Paper [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 2 [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
61,964
|
16,208
|
|
Basis of Fair Value Measurements Level 2 [Member] | Money Market Funds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 2 [Member] | Certificate Of Deposits [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
485
|
|
|
Basis of Fair Value Measurements Level 2 [Member] | Corporate Bonds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
20,160
|
4,690
|
|
Basis of Fair Value Measurements Level 2 [Member] | U.S. Government Securities [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
29,004
|
5,970
|
|
Basis of Fair Value Measurements Level 2 [Member] | Commercial Paper [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
12,315
|
5,548
|
|
Basis of Fair Value Measurements Level 3 [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 3 [Member] | Money Market Funds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 3 [Member] | Certificate Of Deposits [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 3 [Member] | Corporate Bonds [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 3 [Member] | U.S. Government Securities [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|
|
Basis of Fair Value Measurements Level 3 [Member] | Commercial Paper [Member]
|
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Total cash equivalents and marketable securities |
|
|