Shareholder Rights Plan - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Class Of Warrant Or Right [Line Items]
Number of shares of preferred stock authorized | shares	4,991,000
Stockholder rights plan expiration date	2019-01
Exercise price of preferred stock purchase right | $ / shares	$ 20.00
Percentage of Common Stock ownership to make rights exercisable	15.00%
Series B Preferred Stock
Class Of Warrant Or Right [Line Items]
Preferred shares entitled to be purchased per right	0.001