Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Current income tax expense	$ 100,000	$ 900,000	$ 800,000
Tax benefits associated with equity-based compensation	2,609,000	1,845,000	3,837,000
Net operating losses carry forward	3,600,000
Net operating losses valuation allowances	600,000
Tax credits carry forward	5,200,000
Tax credits carry forward, valuation allowances	1,600,000
Net operating losses carry forward expiration dates	2020
Tax credits carry forward expiration dates	2020
Effective tax rate	35.80%	37.20%	37.40%
Expected net tax benefit	$ (2,900,000)