Share Repurchase Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012		Oct. 23, 2013 Subsequent Event [Member]	Sep. 30, 2013 Maximum [Member]	Oct. 23, 2013 Maximum [Member] Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Shares authorized to be repurchased						643,782	800,000
Shares repurchased at cost	$ 7.4	$ 9.9
Shares repurchased	395,000	540,285
Total share outstanding	16,288,597	16,288,597	16,770,232	[1]
Percentage of Shares outstanding authorized to be repurchased under new stock repurchase plan					5.00%

[1] Note: The consolidated balance sheet at December 31, 2012 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U. S. generally accepted accounting principles for complete financial statements. See accompanying notes to the unaudited consolidated financial statements.