Shareholder Rights Plan - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2012
Class of Warrant or Right [Line Items]
Number of shares of preferred stock authorized	4,991,000
Exercise price of preferred stock purchase right	20.00
Percentage of Common Stock owenership to make rights exercisable	15.00%
Series B Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Preferred shares entitled to be purchased per right	0.001