Shareholder Rights Plan - Additional Information (Detail) (USD $)			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Shareholder Rights Plan Two Thousand Eight	Dec. 31, 2012 Shareholder Rights Plan Two Thousand Eight Minimum	Apr. 04, 2008 Shareholder Rights Plan Two Thousand Eight Minimum	Dec. 31, 2012 Shareholder Rights Plan Two Thousand Eight Series B Junior Participating Preferred Stock
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shareholders rights plan exercisability percentage of common stock acquired					15.00%
Shareholders rights plan exercise percentage of voting stock ownership offer					15.00%
Exercise price per right			$ 75.00
Redemption price per right			$ 0.01
Percentage of beneficial ownership				50.00%
Preferred stock , par value	$ 0.01	$ 0.01				$ 0.01
Preferred stock reserved for issuance upon exercise of the rights						175,000