Computation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Options to purchase shares that were not included in the respective computation of diluted EPS because their inclusion would have had an antidilutive effect	62,040	2,579,585	62,040	2,579,585
Options to purchase shares that were not included in the respective computation of diluted EPS because their inclusion would have had an antidilutive effect, weighted average exercise prices	$ 17.95	$ 16.86	$ 17.95	$ 16.86