Weighted Average Contractual Life and Exercise Price (Detail) (Stock Option Plan, USD $)	6 Months Ended
	Jun. 30, 2013
Stock Option Plan
Number of Options
Options outstanding	2,444,557
Options vested	2,407,057
Weighted Average Remaining Contractual Life
Options outstanding	4 years 7 months 6 days
Options vested	4 years 7 months 6 days
Weighted Average Exercise Price
Options outstanding	$ 1.31
Options vested	$ 1.27