Equity (Schedule of stock repurchases) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		0 Months Ended	1 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 25, 2014 Harold W. McGraw III [Member]	Dec. 31, 2013 2013 Repurchase Program	Jun. 30, 2014 2013 Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (in shares)	2.2	1.4	4.4	8.6	0.5	0.1
Repurchase discount					0.35%
Average price paid per share (in dollars per share)	$ 79.65	$ 0.00	$ 79.06	$ 0.00	$ 82.66
Total cash utilized	$ 177	$ 0	$ 352	$ 500	$ 41	$ 10	$ 362