Equity, Stock Repurchase Activities (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stockholders' Equity Note [Abstract]
Stock repurchase program, Authorized amount	$ 1,000,000,000
Stock repurchase program, Remaining authorized repurchase amount	438,300,000
Stock repurchased and retired during period, Shares	6.2	2.4
Common stock repurchased under stock repurchase program average purchase price	$ 20.99	$ 21.75
Common stock repurchased and retired under stock repurchase program, Value	$ 129,900,000	$ 51,600,000