Benefit Plans - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Stock Option Activity [Line Items]
Weighted-Average Exercise Price, Beginning balance	$ 25.35	$ 28.28	$ 29.02
Weighted-Average Exercise Price, Granted	$ 13.87	$ 13.72	$ 10.37
Weighted-Average Exercise Price, Exercised	$ 6.54	$ 6.39	$ 6.02
Weighted-Average Exercise Price, Forfeited	$ 26.21	$ 41.02	$ 30.21
Weighted-Average Exercise Price, Ending balance	$ 25.70	$ 25.35	$ 28.28
Weighted-Average Exercise Price, Options exercisable	$ 29.12	$ 28.00	$ 30.27
Weighted-Average Remaining Contractual Term (years), Ending Balance	5 years 3 months 18 days
Weighted-Average Remaining Contractual Term (years), Options exercisable	4 years 6 months	5 years 2 months 12 days	5 years 9 months 18 days
Aggregate Intrinsic Value, Ending balance	$ 7,877
Aggregate Intrinsic Value, Options exercisable	$ 6,538	$ 5,177	$ 8,035
Employees [Member]
Schedule Of Stock Option Activity [Line Items]
Number of Options Outstanding, Beginning Balance	2,683	3,223	3,330
Number of Options, Granted	345	276	373
Number of Options, Exercised	(266)	(192)	(212)
Number of Options, Forfeited	(166)	(624)	(268)
Number of Options Outstanding, Ending Balance	2,596	2,683	3,223
Number of Options exercisable	2,035	2,230	2,900
Directors [Member]
Schedule Of Stock Option Activity [Line Items]
Number of Options Outstanding, Beginning Balance	10	20	22
Number of Options, Granted	0	0	0
Number of Options, Exercised	0	0	0
Number of Options, Forfeited	(10)	(10)	(2)
Number of Options Outstanding, Ending Balance	0	10	20
Number of Options exercisable	0	10	20