Retirement Plans (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Actual return on plan assets:
Balance at December 31	$ 1,493	$ 1,365
Level 3 [Member]
Fair Value of Financial Assets based on Level 3 inputs held by institutional funds
Balance at January 1	266	194
Actual return on plan assets:
Related to assets held at the end of the year	6	8
Related to assets sold during the year	2	0
Purchases, sales or other settlements	43	66
Net transfers in (out) of Level 3	0	(2)
Balance at December 31	317	266
Fixed Income [Member] | Level 3 [Member]
Fair Value of Financial Assets based on Level 3 inputs held by institutional funds
Balance at January 1	7	8
Actual return on plan assets:
Related to assets held at the end of the year	0	0
Related to assets sold during the year	0	0
Purchases, sales or other settlements	(3)	1
Net transfers in (out) of Level 3	0	(2)
Balance at December 31	4	7
Hedge Funds [Member]
Actual return on plan assets:
Balance at December 31	211	187
Hedge Funds [Member] | Level 3 [Member]
Fair Value of Financial Assets based on Level 3 inputs held by institutional funds
Balance at January 1	187	143
Actual return on plan assets:
Related to assets held at the end of the year	(5)	6
Related to assets sold during the year	2	0
Purchases, sales or other settlements	27	38
Net transfers in (out) of Level 3	0	0
Balance at December 31	211	187
Private Equity Funds [Member]
Actual return on plan assets:
Balance at December 31	58	40
Private Equity Funds [Member] | Level 3 [Member]
Fair Value of Financial Assets based on Level 3 inputs held by institutional funds
Balance at January 1	40	29
Actual return on plan assets:
Related to assets held at the end of the year	9	1
Related to assets sold during the year	0	0
Purchases, sales or other settlements	9	10
Net transfers in (out) of Level 3	0	0
Balance at December 31	58	40
Real Estate Funds [Member]
Actual return on plan assets:
Balance at December 31	51	39
Real Estate Funds [Member] | Level 3 [Member]
Fair Value of Financial Assets based on Level 3 inputs held by institutional funds
Balance at January 1	32	14
Actual return on plan assets:
Related to assets held at the end of the year	2	1
Related to assets sold during the year	0	0
Purchases, sales or other settlements	10	17
Net transfers in (out) of Level 3	0	0
Balance at December 31	$ 44	$ 32