Stockholder's Equity - Additional Information (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013	Mar. 31, 2012
Equity [Abstract]
Common stock, value of shares authorized to repurchase		$ 200,000,000
Stock repurchase, shares		61
Value of shares repurchased		1,668,000
Average price of repurchased shares		$ 27.35
Cash dividend to be paid	$ 0.16	$ 0.16	$ 0.15
Dividend payment to common shareholders		$ 8,448,000	$ 7,877,000
Dividend declared date			May 06, 2013
Dividend to be paid date			Jun. 14, 2013
Dividend declared, shareholders of record date			Jun. 03, 2013