Fair Value Measurements (Fair Value Of Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets:
Available-for-sale securities, fair value	$ 166	$ 172
Foreign exchange derivative contracts		5	[1]
Liabilities:
Foreign exchange derivative contracts	5	15	[1]
Interest agreement derivative contracts	3	3
Level 1 [Member]
Assets:
Foreign exchange derivative contracts		0	[1]
Liabilities:
Foreign exchange derivative contracts	0	0	[1]
Interest agreement derivative contracts	0	0
Level 2 [Member]
Assets:
Foreign exchange derivative contracts		5	[1]
Liabilities:
Foreign exchange derivative contracts	5	15	[1]
Interest agreement derivative contracts	3	3
Level 3 [Member]
Assets:
Foreign exchange derivative contracts		0	[1]
Liabilities:
Foreign exchange derivative contracts	0	0	[1]
Interest agreement derivative contracts	0	0
Sigma Fund Securities [Member]
Assets:
Foreign exchange derivative contracts	1
Sigma Fund Securities [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Sigma Fund securities, fair value	2,944	2,291
Sigma Fund Securities [Member] | Corporate Bonds [Member]
Assets:
Sigma Fund securities, fair value		58
Sigma Fund Securities [Member] | Asset-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		1
Sigma Fund Securities [Member] | Mortgage-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		11
Sigma Fund Securities [Member] | Level 1 [Member]
Assets:
Foreign exchange derivative contracts	0
Sigma Fund Securities [Member] | Level 1 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Sigma Fund securities, fair value	0	0
Sigma Fund Securities [Member] | Level 1 [Member] | Corporate Bonds [Member]
Assets:
Sigma Fund securities, fair value		0
Sigma Fund Securities [Member] | Level 1 [Member] | Asset-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		0
Sigma Fund Securities [Member] | Level 1 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		0
Sigma Fund Securities [Member] | Level 2 [Member]
Assets:
Foreign exchange derivative contracts	1
Sigma Fund Securities [Member] | Level 2 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Sigma Fund securities, fair value	2,944	2,291
Sigma Fund Securities [Member] | Level 2 [Member] | Corporate Bonds [Member]
Assets:
Sigma Fund securities, fair value		43
Sigma Fund Securities [Member] | Level 2 [Member] | Asset-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		1
Sigma Fund Securities [Member] | Level 2 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		11
Sigma Fund Securities [Member] | Level 3 [Member]
Assets:
Foreign exchange derivative contracts	0
Sigma Fund Securities [Member] | Level 3 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Sigma Fund securities, fair value	0	0
Sigma Fund Securities [Member] | Level 3 [Member] | Corporate Bonds [Member]
Assets:
Sigma Fund securities, fair value		15
Sigma Fund Securities [Member] | Level 3 [Member] | Asset-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		0
Sigma Fund Securities [Member] | Level 3 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Sigma Fund securities, fair value		0
Available-For-Sale Securities [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Available-for-sale securities, fair value	16	17
Available-For-Sale Securities [Member] | Corporate Bonds [Member]
Assets:
Available-for-sale securities, fair value	10	11
Available-For-Sale Securities [Member] | Mortgage-Backed Bonds [Member]
Assets:
Available-for-sale securities, fair value	2	3
Available-For-Sale Securities [Member] | Common Stock And Equivalents [Member]
Assets:
Available-for-sale securities, fair value	11	12
Available-For-Sale Securities [Member] | Level 1 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 1 [Member] | Corporate Bonds [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 1 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 1 [Member] | Common Stock And Equivalents [Member]
Assets:
Available-for-sale securities, fair value	3	2
Available-For-Sale Securities [Member] | Level 2 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Available-for-sale securities, fair value	16	17
Available-For-Sale Securities [Member] | Level 2 [Member] | Corporate Bonds [Member]
Assets:
Available-for-sale securities, fair value	10	11
Available-For-Sale Securities [Member] | Level 2 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Available-for-sale securities, fair value	2	3
Available-For-Sale Securities [Member] | Level 2 [Member] | Common Stock And Equivalents [Member]
Assets:
Available-for-sale securities, fair value	8	10
Available-For-Sale Securities [Member] | Level 3 [Member] | U.S. Government And Agency Obligations [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 3 [Member] | Corporate Bonds [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 3 [Member] | Mortgage-Backed Bonds [Member]
Assets:
Available-for-sale securities, fair value	0	0
Available-For-Sale Securities [Member] | Level 3 [Member] | Common Stock And Equivalents [Member]
Assets:
Available-for-sale securities, fair value	$ 0	$ 0

[1] Includes immaterial amounts related to held for sale businesses.