Retirement and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Benefit
Net periodic benefit costs:
Service cost	$ 3	$ 3	$ 7	$ 6
Interest cost	7	7	13	14
Expected return on plan assets	(8)	(8)	(16)	(16)
Recognized actuarial loss	4	5	8	10
Net periodic benefit cost	6	7	12	14
Employer contributions	1	2	2	3
Postretirement Benefit
Net periodic benefit costs:
Service cost	7	6	14	13
Interest cost	10	11	21	22
Recognized actuarial loss	10	9	20	17
Net periodic benefit cost	$ 27	$ 26	$ 55	$ 52