Share Repurchase Plan - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	May. 27, 2015	Oct. 23, 2013
Equity, Class of Treasury Stock [Line Items]
Share Repurchase Plan, Shares repurchased during period, shares		608,757
Shares Repurchase Plan, Share repurchased during period, cost		$ 12.0
Stock Repurchase Plan, Remaining number of shares authorized to be repurchased		1,080,246
Shares, Outstanding		19,530,930
2007 Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share Repurchase Plan, Shares repurchased during period, shares	540,285
Shares Repurchase Plan, Share repurchased during period, cost	$ 9.9
2007 Plan [Member] | Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Share Repurchase Plan, Number of shares authorized to be repurchased	643,782
2013 Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share Repurchase Plan, Number of shares authorized to be repurchased				1,000,000
Share Repurchase Plan, Percentage of shares authorized to be repurchased				5.00%	5.00%
Share Repurchase Plan, Shares repurchased during period, shares			110,997
Shares Repurchase Plan, Share repurchased during period, cost			$ 2.0
2013 Plan [Member] | Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Share Repurchase Plan, Number of shares authorized to be repurchased					800,000