Changes in Stock Options (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise of SARs and stock options, net of surrenders, shares		26,342	56,842
Number of Stock Options, Cancelled		229	8,229
Number of Stock Options, Forfeited			21
Weighted Average Base Price, Exercised		$ 7.08	$ 7.71
Weighted Average Base Price, Cancelled		$ 8.41	$ 10.62
Weighted Average Base Price, Forfeited			$ 8.41
Weighted Average Fair Value, Exercised		$ 5.07	$ 5.73
Weighted Average Fair Value, Cancelled		$ 4.96	$ 8.16
Weighted Average Fair Value, Forfeited			$ 4.96