Changes in Nonvested Stock Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Number of Shares
Nonvested beginning balance	448,426
Granted	222,100
Vested	(157,423)
Forfeited	(55,500)
Nonvested ending balance	457,603
Weighted-Average Grant Date Fair Value
Nonvested beginning balance	$ 7.97
Granted	$ 4.95
Vested	$ 8.19
Forfeited	$ 7.49
Nonvested ending balance	$ 6.49