Significant Components of Deferred Tax Assets and Liabilities (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Deferred revenue	$ 1,988,509	$ 2,072,931
Stock-based compensation expense	1,584,583	1,496,910
Tax credit carry forward	194,364	695,914
Net operating loss carryforward, foreign	2,520,746	1,839,924
Accrued expenses and other	954,559	825,884
Inventory reserve	405,302	417,726
Deferred tax asset	7,648,063	7,349,289
Deferred tax liabilities:
Intangibles related to Srl acquisition	(6,482,404)	(7,594,729)
Depreciation	(6,131,473)	(5,210,775)
Deferred tax liability	$ (12,613,877)	$ (12,805,504)