Stock Based Compensation - Options Granted to Executives Non Executives and Directors that are Exercisable or Expected to Vest in Future (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares - Exercisable or Expected to Vest in Future	5,798,797
Weighted Average Exercise Price - Exercisable or Expected to Vest in Future	$ 41.47
Number of Shares - Exercisable or Expected to Vest in Future	8 years 2 months 23 days
Weighted Average Exercise Price - Exercisable or Expected to Vest in Future	$ 3,669
Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares - Exercisable or Expected to Vest in Future	4,475,604
Weighted Average Exercise Price - Exercisable or Expected to Vest in Future	$ 41.03
Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares - Exercisable or Expected to Vest in Future	1,044,000
Weighted Average Exercise Price - Exercisable or Expected to Vest in Future	$ 44.46
Non-Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares - Exercisable or Expected to Vest in Future	279,193
Weighted Average Exercise Price - Exercisable or Expected to Vest in Future	$ 37.36