Taxes - Constituents of Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current deferred tax assets:
Inventory and revenue related	$ 4,303	$ 5,202
Bonuses, commissions, and other compensation	1,280	1,273
Other	1,093	1,283
Gross current deferred tax assets	6,676	7,758
Valuation allowance	(307)	(878)
Net current deferred tax assets	6,369	6,880
Noncurrent deferred tax assets:
Federal and state tax credit carryforwards	9,747	12,274
Stock-based compensation expense	7,242	6,160
Depreciation	1,819	1,798
Acquired completed technologies and other intangible assets	1,119	1,519
Unrealized investment gains and losses	1,075	891
Correlative tax relief and deferred interest related to reserves	520	609
Capital loss carryforward	373	373
Acquired in-process technology	90	178
Other	1,960	1,928
Gross noncurrent deferred tax assets	23,945	25,730
Noncurrent deferred tax liabilities:
Nondeductible intangible assets	(4,945)	(6,244)
Other	(2,171)	(1,045)
Gross noncurrent deferred tax liabilities	(7,116)	(7,289)
Valuation allowance	(1,182)	(2,522)
Net noncurrent deferred tax assets	$ 15,647	$ 15,919