Fair Value Measurements (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 38,199	$ 77,053
Short-term investments	19,063	18,471
Total assets	57,262	95,524
Level 1 Inputs
Assets:
Cash and cash equivalents	38,199	77,053
Short-term investments	19,063	18,471
Total assets	57,262	95,524
Level 2 Inputs
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Total assets	0	0
Level 3 Inputs
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Total assets	$ 0	$ 0