Shareholders' Equity Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stockholders Equity Note [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.48
Repurchase and retirement of common stock			$ 3,970
Repurchase and retirement of common stock, shares	30
Shares remaining available for repurchases	1,574		1,574
Cash dividend paid during period, per share	$ 0.48	$ 0.42	$ 1.44	$ 1.26
Common stock excluded from calculation of diluted earnings per share	647	67	562	870