Employee Benefits (Details 5) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	$ 1,851		$ 1,505
Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	650		732
Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	1,183		750
Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	18		23
Cash and short-term investments, and other [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	180		32
Cash and short-term investments, and other [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	2		2
Cash and short-term investments, and other [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	178		30
Cash and short-term investments, and other [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0		0
US indexed equity securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	399	[1]	306	[1]
US indexed equity securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	119	[1]	125	[1]
US indexed equity securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	280	[1]	181	[1]
US indexed equity securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[1]	0	[1]
US growth and value securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	344		370
US growth and value securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	307		370
US growth and value securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	37		0
US growth and value securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0		0
UK equity securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	154		144
UK equity securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	85		78
UK equity securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	69		66
UK equity securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0		0
International equity securities excluding UK [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	225		297
International equity securities excluding UK [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	137		157
International equity securities excluding UK [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	87		139
International equity securities excluding UK [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	1		1
Long duration bonds [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	370	[2]	195	[2]
Long duration bonds [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[2]	0	[2]
Long duration bonds [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	370	[2]	195	[2]
Long duration bonds [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[2]	0	[2]
Intermediate Duration Securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	3
Intermediate Duration Securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Intermediate Duration Securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	3
Intermediate Duration Securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Agency mortgage backed securities
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	13
Agency mortgage backed securities | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Agency mortgage backed securities | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	13
Agency mortgage backed securities | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Asset-backed Securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	10
Asset-backed Securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Asset-backed Securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	10
Asset-backed Securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0
Non-agency mortgage backed securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	52	[3]	66	[3]
Non-agency mortgage backed securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[3]	0	[3]
Non-agency mortgage backed securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	52	[3]	66	[3]
Non-agency mortgage backed securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[3]	0	[3]
UK fixed income securities [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	41	[4]	45	[4]
UK fixed income securities [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[4]	0	[4]
UK fixed income securities [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	41	[4]	45	[4]
UK fixed income securities [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[4]	0	[4]
International fixed income securities excluding UK [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	43		28
International fixed income securities excluding UK [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0		0
International fixed income securities excluding UK [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	43		28
International fixed income securities excluding UK [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0		0
Real estate UK [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	17	[5]	22	[5]
Real estate UK [Member] | Level 1 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[5]	0	[5]
Real estate UK [Member] | Level 2 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	0	[5]	0	[5]
Real estate UK [Member] | Level 3 [Member]
Fair value of defined benefit plans assets by asset class
Fair value of defined benefit plans assets by asset class, Total	$ 17	[5]	$ 22	[5]

[1] Includes securities that are tracked in the following indexes: S&P 500, S&P MidCap 400, S&P MidCap 400 Growth and S&P Smallcap 600.

[2] Includes securities that are investment grade obligations of issuers in the U.S.

[3] Includes U.S. mortgage-backed securities that are not backed by the U.S. government.

[4] Includes securities originated by the government of and other issuers from the U.K.

[5] Includes a fund which holds real estate properties in the U.K.