Retirement and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Benefit
Net periodic benefit costs:
Service cost	$ 4	$ 3
Interest cost	6	7
Expected return on plan assets	(8)	(8)
Recognized actuarial loss	4	5
Net periodic benefit cost	6	7
Employer contributions	1	1
Postretirement Benefit
Net periodic benefit costs:
Service cost	7	7
Interest cost	11	11
Recognized actuarial loss	10	8
Net periodic benefit cost	$ 28	$ 26