Equity, Stock Repurchase Activities (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended
	Jul. 23, 2014	Mar. 31, 2015	Mar. 31, 2014 agreement institution	Oct. 31, 2014	Feb. 28, 2014
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount				$ 3,400,000,000	$ 2,100,000,000
Stock repurchased and retired		17.4
Common stock repurchased under stock repurchase program average purchase price (in dollars per share)		$ 23.05
Common stock repurchased and retired under stock repurchase program, value		400,000,000	900,000,000
Number of accelerated share repurchase agreements			2
Number of financial institutions for ASR			2
Accelerated share repurchases, aggregate payments made during period			1,200,000,000
Shares repurchased under ASR	16.0
Accelerated share repurchases, shares repurchased	49.3
Accelerated share repurchases, weighted average repurchase price (in USD per share)	$ 24.35
Intended stock repurchases		600,000,000
2014 Stock Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount			1,200,000,000
Additional amount authorized under Stock Repurchase Plan				1,300,000,000
Stock repurchased and retired			33.3
Accelerated share repurchases, remaining amount recorded in equity	300,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 775,000,000