Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 25, 2014	Dec. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 04, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Value, Acquired, Cost Method					$ 273
Treasury Stock Acquired, Average Cost Per Share			$ 104.82	$ 79.65	$ 104.62	$ 79.06
Interest in joint venture minimum percentage					20.00%
Agreement terms, change of control, put option for minority interest ownership, effective period					15 days
2013 Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Value, Acquired, Cost Method		$ 10				$ 362
Stock repurchase program number of shares authorized to be repurchased (in shares)							50,000,000
Maximum number of shares authorized for repurchase under stock repurchase plan as percentage of outstanding common stock							18.00%
Remaining shares available under repurchase program (in shares)			42,900,000		42,900,000
Harold W. McGraw III [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 41
Treasury Stock Acquired, Average Cost Per Share	$ 82.66