Capital Transactions (Details) (USD $)	1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended
	Feb. 03, 2011 Share Repurchase Program	Jun. 30, 2012 Share Repurchase Program	Feb. 02, 2012 New Share Repurchase Program	Jun. 30, 2013 New Share Repurchase Program	Jun. 30, 2012 New Share Repurchase Program
Share Repurchase Program [Line Items]
Stock repurchase program, dollar amount authorized	$ 1,500,000,000		$ 1,000,000,000
Cost of common stock repurchased and retired under the stock repurchase program		$ 261,000,000		$ 0	$ 54,000,000
Shares of common stock repurchased and retired		22,000,000		0	4,000,000