Condensed Balance Sheets (Parenthetical) (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Par value of common stock issued	$ 0.0001	$ 0.0001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	30,084,883	30,036,481
Common stock, shares outstanding	29,820,836	29,772,434
Treasury stock, shares	264,047	264,047
Parent Company
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Par value of common stock issued	$ 0.0001	$ 0.0001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	30,084,883	30,036,481
Common stock, shares outstanding	29,820,836	29,772,434
Treasury stock, shares	264,047	264,047