Stockholder's Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended			0 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jul. 25, 2011	Oct. 27, 2014 Subsequent Event [Member]
Stockholders Equity [Line Items]
Common stock, value of shares authorized to repurchase							$ 200,000
Stock repurchase, shares					728,000
Value of shares repurchased					20,809
Average price of repurchased shares					$ 28.59
Cash dividend paid	$ 0.165	$ 0.165	$ 0.160	$ 0.160	$ 0.490	$ 0.480
Dividend payment to common shareholders					$ 26,081	$ 25,458
Dividend declared date					Oct. 27, 2014
Cash dividend to be paid								$ 0.165
Dividend to be paid date					Dec. 12, 2014
Dividend declared, shareholders of record date					Dec. 01, 2014