Fair Value Measurements (U.S. Plans) (Details) - U.S. Pension Benefit Plans - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Accrued income receivable	$ 9	$ 3
Fair value plan assets	3,130	3,317	$ 6,071
Common stock and equivalents
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	89	902
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	1,541	565
Preferred stock
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	2	3
Government, agency and government-sponsored enterprise obligations
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	120	520
Other government bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	70	91
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	862	795
Mortgage-backed bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	2	16
Commingled short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	435	422
Total Investment securities
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	3,121	3,314
Level 1 | Common stock and equivalents
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	89	902
Level 1 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Preferred stock
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	2	3
Level 1 | Government, agency and government-sponsored enterprise obligations
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Other government bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Mortgage-backed bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Commingled short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 1 | Total Investment securities
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	91	905
Level 2 | Common stock and equivalents
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 2 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	1,541	565
Level 2 | Preferred stock
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	0	0
Level 2 | Government, agency and government-sponsored enterprise obligations
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	120	520
Level 2 | Other government bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	70	91
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	862	795
Level 2 | Mortgage-backed bonds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	2	16
Level 2 | Commingled short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	435	422
Level 2 | Total Investment securities
Defined Benefit Plan Disclosure [Line Items]
Total investments securities	$ 3,030	$ 2,409