Shareholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Stockholders Equity Note [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.42
Repurchase and retirement of common stock			$ 31,907
Repurchase and retirement of common stock, shares			373,000
Shares remaining available for repurchases	1,608,000		1,608,000
Cash dividend paid during period, per share	$ 0.42	$ 0.37	$ 1.26	$ 1.11
Common stock excluded from calculation of diluted earnings per share	67,000	917,000	870,000	1,148,000