Employee Benefit Plans - Level 3 Rollforward (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Domestic Pension Plans [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	$ 1,655		$ 1,486		$ 1,506
Domestic Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	122	[1]	95	[1]
Domestic Pension Plans [Member] | Limited Partnership Interests [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	96	[2]	71	[2]
Domestic Pension Plans [Member] | Limited Partnership Interests [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning of year	71	[1],[2]	84		80
Defined Benefit Plan, Actual Return on Plan Assets Still Held	7		7		10
Defined Benefit Plan, Purchases, Sales, and Settlements	18		(20)		(6)
Fair Value of Plan Assets, End of year	96	[1],[2]	71	[1],[2]	84
Domestic Pension Plans [Member] | Real Estate Funds [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	26		24
Domestic Pension Plans [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning of year	24	[1]	17		15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	2		4		2
Defined Benefit Plan, Purchases, Sales, and Settlements	0		3		0
Fair Value of Plan Assets, End of year	26	[1]	24	[1]	17
Domestic Other Postretirement Plans [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	650		597		605
Domestic Other Postretirement Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	7	[1]	6	[1]
Domestic Other Postretirement Plans [Member] | Limited Partnership Interests [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	7	[2]	6	[2]
Domestic Other Postretirement Plans [Member] | Limited Partnership Interests [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning of year	6	[1],[2]	7		8
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1		1		0
Defined Benefit Plan, Purchases, Sales, and Settlements	0		(2)		(1)
Fair Value of Plan Assets, End of year	7	[1],[2]	6	[1],[2]	7
UK Pension Plans [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning of year	1,759		1,633
Foreign Currency Exchange Rate Changes	88		(13)
Fair Value of Plan Assets, End of year	1,996		1,759
UK Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	163	[1]	158	[1]
UK Pension Plans [Member] | Real Estate Funds [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, End of year	163		158
UK Pension Plans [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning of year	158	[1]	148		133
Defined Benefit Plan, Actual Return on Plan Assets Still Held	(3)		11		19
Foreign Currency Exchange Rate Changes	8		(1)		(4)
Fair Value of Plan Assets, End of year	$ 163	[1]	$ 158	[1]	$ 148

[1] Refer to Note 15 for additional discussion regarding the three levels of the fair value hierarchy.

[2] Limited partnership interests include several funds that invest primarily in buyout, growth equity and venture capital.