Issued and Outstanding Stock Options (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Long-Term Stock Incentive Plans:
Options outstanding at the beginning of period			6,216,805	6,891,975
Granted			7,500	7,500
Exercised	(50,000)	(134,000)	(443,669)	(596,470)
Forfeited			(2,450)
Expired				(3,750)
Options outstanding at the end of period	5,778,186	6,299,255	5,778,186	6,299,255
Options exercisable at the end of the period	5,147,624	4,534,143	5,147,624	4,534,143
Options outstanding at the beginning of period, weighted average exercise price			$ 15.57	$ 15.20
Granted			$ 17.11	$ 18.67
Exercised			$ 13.65	$ 13.18
Forfeited			$ 16.15
Expired				$ 12.15
Options outstanding at the end of period, weighted average exercise price	$ 15.72	$ 15.54	$ 15.72	$ 15.54
Options exercisable at the end of the period, exercise price	$ 16.02	$ 16.12	$ 16.02	$ 16.12