Equity (Treasury Stock) - Additional Information (Detail) - USD ($)		3 Months Ended			6 Months Ended	9 Months Ended
	Apr. 12, 2016	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Apr. 12, 2016	Sep. 30, 2015	Dec. 31, 2013
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock				$ 182,000,000
Accelerated Share Repurchase Agreement [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired			25,700,000
Value of treasury stock acquired, cost method			$ 600,000,000
Aggregate authorized amount of common stock to be repurchased			750,000,000				$ 750,000,000
Payments for repurchase of common stock			750,000,000
Accelerated stock repurchases not yet settled			150,000,000
Accelerated Share Repurchase Agreement [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired	9,400,000
2013 Repurchase Program [Member] | Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Aggregate authorized amount of common stock to be repurchased								$ 500,000,000
2013 Repurchase Program And Open Market Repurchases [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired							14,300,000
Value of treasury stock acquired, cost method							$ 406,500,000
2015 Repurchase Program [Member] | Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Aggregate authorized amount of common stock to be repurchased			$ 1,250,000,000				$ 1,250,000,000
2015 Repurchase Program And Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired					19,200,000
Value of treasury stock acquired, cost method					$ 449,900,000
2015 Repurchase Plan Open Market Purchases And Accelerated Share Repurchase Agreement [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired						54,300,000
Value of treasury stock acquired, cost method						$ 1,200,000,000
Treasury stock remaining authorized repurchase amount	$ 50,100,000					$ 50,100,000
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] | Treasury Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired		345,965		328,358
Value of treasury stock acquired, cost method		$ 7,100,000		$ 9,500,000