Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension [Member]
Components of net pension and postretirement benefits costs
Service cost of benefits earned	$ 9	$ 10
Interest cost on projected benefit obligation	16	16
Expected return on plan assets	(20)	(19)
Net amortization	6	11
Net (benefit) cost	11	18
Postretirement [Member]
Components of net pension and postretirement benefits costs
Service cost of benefits earned	1	1
Interest cost on projected benefit obligation	2	2
Net amortization	(9)	(9)
Net (benefit) cost	$ (6)	$ (6)