Goodwill and Intangible Assets Net - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
Disposal or recognition of additional goodwill									$ 0
Impairment charges on goodwill									0
Goodwill balance	1,316,000				1,316,000				1,316,000	1,316,000
Amortization expenses of intangible assets	51,000	50,000	51,000	50,000	50,000	51,000	51,000	50,000	202,000	202,000	67,000
Impairment charges recognized related to the acquired intangible assets									0	0
Annual amortization expense of the intangible assets, 2012	200,000								200,000
Annual amortization expense of the intangible assets, 2013	200,000								200,000
Annual amortization expense of the intangible assets, 2014	200,000								200,000
Annual amortization expense of the intangible assets, 2015	200,000								200,000
Annual amortization expense of the intangible assets, 2016	200,000								200,000
Annual amortization expense of the intangible assets, 2017	200,000								200,000
Annual amortization expense of the intangible assets, 2018	200,000								200,000
Annual amortization expense of the intangible assets, 2019	200,000								200,000
Annual amortization expense of the intangible assets, 2020	$ 100,000								$ 100,000