Fair Value Measurements (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 22,511	$ 79,276
Short-term investments	416	16,248
Total assets	22,927	95,524
Liabilities:
Contingent consideration	9,921	16,450
Total liabilities	9,921	16,450
Level 1 Inputs
Assets:
Cash and cash equivalents	22,511	79,276
Short-term investments	416	16,248
Total assets	22,927	95,524
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
Level 2 Inputs
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Total assets	0	0
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
Level 3 Inputs
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Total assets	0	0
Liabilities:
Contingent consideration	9,921	16,450
Total liabilities	$ 9,921	$ 16,450