Employee Retirement Plans (Summary Of The Components Of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Components Of Net Periodic Benefit Expense [Line Items]
Service cost	$ 62	$ 53	$ 46
Interest cost	154	153	157
Expected return on plan assets	(157)	(161)	(168)
Amortization of net loss	72	79	50
Amortization of prior service cost (credit)	8	9	9
Total periodic benefit expense	139	133	94
Curtailment charge			(1)
Total expense	139	133	93
Curtailment effects			1
Current year actuarial loss (gain)	257	107	106
Amortization of actuarial loss	(72)	(79)	(50)
Current year prior service (credit)/ loss	3	3	23
Amortization of prior service (cost) credit	(8)	(9)	(9)
Total recognized in other comprehensive income (loss)	180	22	71
Total recognized in net periodic benefit cost and other comprehensive income	319	155	164
Postretirement Benefits [Member]
Components Of Net Periodic Benefit Expense [Line Items]
Service cost	13	13	12
Interest cost	45	49	50
Amortization of net loss	15	18	15
Amortization of prior service cost (credit)	(6)	(6)	(6)
Total periodic benefit expense	67	74	71
Total expense	67	74	71
Current year actuarial loss (gain)	20	(31)	77
Amortization of actuarial loss	(16)	(18)	(15)
Current year prior service (credit)/ loss			(31)
Amortization of prior service (cost) credit	6	6	6
Total recognized in other comprehensive income (loss)	10	(43)	37
Total recognized in net periodic benefit cost and other comprehensive income	$ 77	$ 31	$ 108