Employee Benefit Plans (Details 2) (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 Benefits [Member]
Components of net periodic benefit cost:
Service cost	$ 11	$ 9	$ 22	$ 19
Interest cost	13	14	26	28
Expected return on plan assets	(15)	(16)	(30)	(32)
Amortization of net actuarial loss	15	14	30	27
Net actuarial loss from settlements	0	2	0	2
Net periodic benefit cost	24	23	48	44
Other Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	0	0	1	1
Interest cost	3	3	6	6
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of prior service cost (credit)	(2)	(1)	(4)	(3)
Amortization of net actuarial loss	1	1	3	4
Net periodic benefit cost	$ 0	$ 1	$ 2	$ 4