Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension [Member]
Components of net pension and postretirement benefits costs
Service cost of benefits earned	$ 9	$ 9	$ 18	$ 19
Interest cost on projected benefit obligation	17	16	33	31
Expected return on plan assets	(20)	(19)	(40)	(38)
Net amortization	6	12	12	23
Net (benefit) cost	12	18	23	35
Postretirement [Member]
Components of net pension and postretirement benefits costs
Service cost of benefits earned	0	1	1	2
Interest cost on projected benefit obligation	2	2	4	3
Net amortization	(9)	(9)	(18)	(17)
Net (benefit) cost	$ (7)	$ (6)	$ (13)	$ (12)