Fair Value Measurements (U.S. Plans) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Common Stock and Equivalents | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	$ 1,595
Level 1
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	44	38
Level 1 | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,601	1,137
Level 1 | Common Stock and Equivalents
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	44	38
Level 1 | Common Stock and Equivalents | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,592	1,128
Level 1 | Commingled Equity Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 1 | Commingled Equity Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Preferred Stock | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	9	9
Level 1 | U.S. Government And Agency Obligations
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 1 | U.S. Government And Agency Obligations | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Other Government Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Corporate Bonds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 1 | Corporate Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Mortgage-backed Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Commingled Bond Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 1 | Commingled Bond Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 1 | Commingled Short-Term Investment Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 1 | Commingled Short-Term Investment Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 2
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	111	117
Level 2 | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	3,815	3,599
Level 2 | Common Stock and Equivalents
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	0	0
Level 2 | Common Stock and Equivalents | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	3	3
Level 2 | Commingled Equity Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	56	54
Level 2 | Commingled Equity Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,965	1,705
Level 2 | Preferred Stock | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	0	0
Level 2 | U.S. Government And Agency Obligations
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	9	10
Level 2 | U.S. Government And Agency Obligations | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	317	261
Level 2 | Other Government Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	49	40
Level 2 | Corporate Bonds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	9	11
Level 2 | Corporate Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	327	322
Level 2 | Mortgage-backed Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	14	18
Level 2 | Commingled Bond Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	30	34
Level 2 | Commingled Bond Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,082	1,018
Level 2 | Commingled Short-Term Investment Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	6	7
Level 2 | Commingled Short-Term Investment Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	58	232
Total
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	155	155
Total | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	5,416	4,736
Accrued income receivable	10	11
Fair value plan assets	5,426	4,747
Total | Common Stock and Equivalents
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	44	38
Total | Common Stock and Equivalents | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities		1,131
Total | Commingled Equity Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	56	54
Total | Commingled Equity Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,965	1,705
Total | Preferred Stock | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	9	9
Total | U.S. Government And Agency Obligations
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	9	10
Total | U.S. Government And Agency Obligations | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	317	261
Total | Other Government Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	49	40
Total | Corporate Bonds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	9	11
Total | Corporate Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	327	322
Total | Mortgage-backed Bonds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	14	18
Total | Commingled Bond Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	30	34
Total | Commingled Bond Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	1,082	1,018
Total | Commingled Short-Term Investment Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value plan assets	6	7
Total | Commingled Short-Term Investment Funds | U.S. Plans
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total investment securities	$ 58	$ 232