Retirement and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefit
Net periodic benefit costs:
Service cost	$ 3	$ 3	$ 10	$ 9
Interest cost	6	6	19	20
Expected return on plan assets	(7)	(7)	(23)	(23)
Amortization of prior service cost		1		1
Recognized actuarial loss	10	4	18	14
Net periodic benefit cost	12	7	24	21
Employer contributions	1	1	3	4
Postretirement Benefit
Net periodic benefit costs:
Service cost	8	6	22	19
Interest cost	11	10	32	32
Recognized actuarial loss	9	10	29	27
Net periodic benefit cost	$ 28	$ 26	$ 83	$ 78