Summary Of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shares Under Option
Shares Under Option, Outstanding Beginning Balance	1,384,537	1,875,170	2,388,684
Shares Under Option, Granted
Shares Under Option, Exercised	(645,745)	(52,589)	(313,514)
Shares Under Option, Forfeited		(438,044)	(200,000)
Shares Under Option, Expired
Shares Under Option, Outstanding Ending Balance	738,792	1,384,537	1,875,170	2,388,684
Shares Under Option, Ending vested and expected to vest at December 31, 2012	738,792
Share under Option, Exercisable	162,792	396,985	257,040
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Outstanding Beginning Balance	$ 17.58	$ 17.53	$ 17.03
Weighted-Average Exercise Price, Granted
Weighted-Average Exercise Price, Exercised	$ 16.64	$ 18.48	$ 13.13
Weighted-Average Exercise Price, Forfeited		$ 17.28	$ 18.48
Weighted-Average Exercise Price, Expired
Weighted-Average Exercise Price, Outstanding Ending Balance	$ 18.39	$ 17.58	$ 17.53	$ 17.03
Weighted-Average Exercise Price, Ending vested and expected to vest	$ 18.39
Weighted-Average Exercise Price, Exercisable	$ 17.82	$ 18.16	$ 17.92
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term, Outstanding	4 years 10 months 24 days	4 years 4 months 24 days	5 years 4 months 24 days	6 years 1 month 6 days
Weighted-Average Remaining Contractual Term, Ending vested and expected to vest	4 years 10 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years	5 years 4 months 24 days	6 years
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 14,587	$ 17,147	$ 21,629
Aggregate Intrinsic Value, Outstanding Ending balance	8,891	14,587	17,147	21,629
Aggregate Intrinsic Value, Ending vested and expected to vest	8,891
Aggregate Intrinsic Value, Exercisable	$ 1,243	$ 1,774	$ 1,546