Share Capital (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 02, 2011	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Treasury stock repurchase limit						$ 1,000,000,000
Treasury Stock, Shares, Retired (in Shares)	7,300,000	4,300,000	7,300,000			6,900,000
Treasury Stock, Retired, Cost Method, Amount	157,700,000	92,300,000	165,600,000			144,000,000
Treasury Stock, Value, Acquired, Cost Method	440,400,000
Stock Repurchased and Retired During Period, Shares (in Shares)				2,876,000
Preferred Stock, Liquidation Preference Per Share (in Dollars per share)		$ 25.00		$ 25.00
Payments for Repurchase of Redeemable Preferred Stock					94,157,000
Noncontrolling Interest, Period Increase (Decrease)			130,000
Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Unit Grants In Period (in Shares)				1,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)				$ 9,820,000
Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Units Grants In Period Weighted Average Grant Date Fair Value				24,600,000
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures (in Shares)				40,944
Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Awards Grants In Period Weighted Average Grant Date Fair Value				1,000,000
Minimum Percentage Target Pay out Under Performance Unit Grants In Period				0.00%
Maximum Percentage Target Pay out Under Performance Unit Grants In Period				200.00%
Performance Incentive Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Units Grants In Period Weighted Average Grant Date Fair Value				29,400,000
Share Based Compensation Arrangement By Share Based Payment Award Performance Unit Grants In Period				1,300,000
Maximum Limit Share Pay out Under Performance Unit Grants In Period				2,600,000
Series C Preferred Stock [Member]
Stock Repurchased and Retired During Period, Shares (in Shares)			30,000		4,400,000
Liquidation value of preferred shares repurchased			750,000		110,800,000
Payments for Repurchase of Redeemable Preferred Stock			650,000		94,200,000
Book value gain on repurchase of preferred stock					16,600,000
Series E Preferred Stock [Member]
Stock Repurchased and Retired During Period, Shares (in Shares)			500
Liquidation value of preferred shares repurchased			500,000
Payments for Repurchase of Preferred Stock and Preference Stock			$ 470,000