Shares Repurchase (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Total number of Shares Repurchased	29		2,498	537	2,798
Prices Paid Per Share, Low Range	$ 14.98		$ 12.46	$ 13.85	$ 12.46
Prices paid per share, High range	$ 14.98		$ 16.10	$ 15.00	$ 18.53
Total Cost of Shares Repurchased	$ 447	$ 7,316	$ 37,165	$ 7,908	$ 42,677