Restricted Stock Units Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012
Number of Units
Outstanding at beginning of period	34,738
Granted	39,237
Forfeited	(1,773)
Outstanding at end of period	72,202
Exercisable at end of period	0
Vested and expected to vest in the future at end of period	50,067
Weighted Average Remaining Contractual Life (in years)
Outstanding at end of period	2 years 8 months 9 days
Exercisable at end of period	0 years
Vested and expected to vest in the future at end of period	2 years 2 months 19 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 6,533,061
Exercisable at end of period	0.00
Vested and expected to vest in the future at end of period	$ 4,530,198