Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension
Components of net pension and postretirement benefits costs
Service cost of benefits earned	$ 9	$ 10	$ 27	$ 29
Interest cost on projected benefit obligation	16	16	49	47
Expected return on plan assets	(20)	(19)	(60)	(57)
Net amortization	7	11	19	34
Net pension cost	12	18	35	53
Postretirement
Components of net pension and postretirement benefits costs
Service cost of benefits earned	1	1	2	3
Interest cost on projected benefit obligation	1	2	5	5
Net amortization	(8)	(9)	(26)	(26)
Net pension cost	$ (6)	$ (6)	$ (19)	$ (18)