Assets and Liabilities Recorded at Fair Value on Recurring Basis on Condensed Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Assets:
Cash and cash equivalents	$ 5,840	$ 4,150	$ 4,074	$ 4,114
Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	5,840	4,150
Corporate notes and bonds	2,015	6,871
U.S. Government and agency securities	1,423	4,189
Total assets at fair value	9,341	15,255
Fair Value, Measurements, Recurring | Equity Security
Assets:
Total assets at fair value	63	45
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)
Assets:
Cash and cash equivalents	5,840	4,150
Corporate notes and bonds	0	0
U.S. Government and agency securities	0	0
Total assets at fair value	5,903	4,195
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) | Equity Security
Assets:
Total assets at fair value	63	45
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Corporate notes and bonds	2,015	6,871
U.S. Government and agency securities	1,423	4,189
Total assets at fair value	3,438	11,060
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity Security
Assets:
Total assets at fair value	$ 0	$ 0