Stock-Based Compensation - Summary of Stock Incentive Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning of year, Shares	335,730	416,886	566,323
Granted, Shares	522,357	88,307	57,723
Exercised, Shares	(118,438)	(71,055)	(85,379)
Forfeited, Shares	(13,081)		(12,666)
Expired, Shares	(13,990)	(98,408)	(109,115)
Outstanding at end of year, Shares	712,578	335,730	416,886
Exercisable at end of year, Shares	103,549	178,432	304,628
Weighted-average fair value of awards granted, Shares	$ 13.94	$ 12.50	$ 14.06
Outstanding at beginning of year, Weighted-Average Exercise Price	$ 42.14	$ 43.52	$ 42.84
Granted, Weighted-Average Exercise Price	$ 49.09	$ 39.66	$ 44.15
Exercised, Weighted-Average Exercise Price	$ 39.39	$ 30.78	$ 18.94
Forfeited, Weighted-Average Exercise Price	$ 47.50		$ 40.85
Expired, Weighted-Average Exercise Price	$ 49.08	$ 53.99	$ 59.85
Outstanding at end of year, Weighted-Average Exercise Price	$ 47.42	$ 42.14	$ 43.52
Exercisable at end of year, Weighted-Average Exercise Price	$ 46.02	$ 45.28	$ 46.27