Shareholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended		0 Months Ended	3 Months Ended
	Dec. 31, 2014 Vote	Dec. 31, 2012	Dec. 31, 2014 Vote	Dec. 31, 2013	Jul. 31, 2013	Sep. 29, 2013	Sep. 30, 2013	Dec. 05, 2008 Right	Apr. 27, 2008	Nov. 27, 2011	Apr. 29, 2014
Class of Stock [Line Items]
Authorized shares	400,000		400,000
Preferred stock Par value (in dollars per share)	$ 0.01		$ 0.01
Vote entitled for each common share outstanding	1		1
Common stock par value, in dollars per share	$ 0.002		$ 0.002	$ 0.002			$ 0.002
Number of preferred stock purchase right for dividend distribution								1
Outstanding common share to be acquiring person	15.00%		15.00%
Stock Repurchased During Period, Value			$ 59,673,000	$ 47,908,000
Cash dividend declared per common share	$ 0	$ 0.055
Special dividend declared and paid		$ 0.50
Common Stock [Member]
Class of Stock [Line Items]
Stock split ratio					2	2
Common Stock [Member] | Repurchase Program 2008 [Member]
Class of Stock [Line Items]
Repurchase of authorized common stock									50,000,000
Common Stock [Member] | Repurchase Program 2011 [Member]
Class of Stock [Line Items]
Repurchase of authorized common stock										80,000,000
Aggregate stock repurchased, shares	2,243,000		2,243,000
Aggregate stock repurchased, value	80,000,000		80,000,000
Stock Repurchased During Period, Shares			1,351,000
Stock Repurchased During Period, Value			52,095,000
Common Stock [Member] | Repurchase Program 2014 [Member]
Class of Stock [Line Items]
Repurchase of authorized common stock											50,000,000
Stock Repurchased During Period, Shares			183,000
Stock Repurchased During Period, Value			$ 7,578,000