Shareholders' Equity - Additional Information (Detail) (USD $)	12 Months Ended			115 Months Ended													12 Months Ended	132 Months Ended		12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Nov. 30, 1993 Non-Discretionary Plan	Nov. 30, 2001 Discretionary Plan	Dec. 31, 2011 Stock Option Plan 1985	Dec. 31, 2010 Stock Option Plan 1985	Dec. 31, 2009 Stock Option Plan 1985	Dec. 31, 2008 Stock Option Plan 1985	Dec. 31, 2009 Stock Option Plan 2008	Dec. 31, 2008 Stock Option Plan 2008	Dec. 31, 2010 Stock Option Plan 2009	Dec. 31, 2009 Stock Option Plan 2009	Dec. 31, 2011 Stock Option Plan 2010	Dec. 31, 2010 Stock Option Plan 2010	Dec. 31, 2011 Stock Option Plan 2011	Dec. 31, 2011 Stock Option Plan 2011	May 04, 2011 Stock Option Plan 2011	Dec. 31, 2011 Stock Option Plan 2011 Maximum	Dec. 31, 2011 Employee Stock Purchase Plan	Dec. 31, 2010 Employee Stock Purchase Plan	Dec. 31, 2009 Employee Stock Purchase Plan	Dec. 31, 2011 Directors' Restricted Stock Plan 2008	May 31, 2008 Directors' Restricted Stock Plan 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Share authorized for repurchase					40,000,000
Expected Common Stock Shares Issued and Outstanding						200,000,000
Shares authorized for grant														3,000,000		3,000,000	3,000,000	3,000,000	3,000,000		9,305,452				200,000
Grants, maximum number of shares per person																	100,000
Award vesting period																				5 years				1 year
Maximum Contractual Term																		10 years
Purchase Price Percentage of Fair Market Value																					85.00%
Issuance of shares under stock purchase plan				6,565,359
Amount withheld Employee Stock Purchase Plan																					$ 13,419,000
Fair Value of Annual Grant per Participant of Restricted Stock Awards																								200,000
Shares available for granting of awards							6,912	6,912	6,912	6,912	0	911,585	0	550,800	0	365,115	1,610	1,610						99,402
Restricted shares granted																								19,500
Weighted average fair value of award granted during the period																					$ 11.70	$ 11.16	$ 12.78	$ 51.27
Total intrinsic value of options exercised	47,000,000	135,000,000	38,000,000
Total Unrecognized Share-Based compensation cost	$ 92,000,000			$ 92,000,000
Unrecognized Share-Based compensation cost, weighted average period	3.2