Pensions, Other Post-employment Benefits and Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Net Periodic Benefit Cost [Line Items]
Service cost	$ 5	$ 4
Interest cost	16	19
Expected return on plan assets	(17)	(18)
Amortization of actuarial losses	7	2
Amortization of prior service credit	0	0
Net periodic benefit cost	11	7
OPEB
Net Periodic Benefit Cost [Line Items]
Service cost	0	0
Interest cost	3	3
Expected return on plan assets	0	0
Amortization of actuarial losses	2	1
Amortization of prior service credit	(1)	(1)
Net periodic benefit cost	$ 4	$ 3