Employee Benefit Plans (Details 6) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value Measurements of Company's Pension Plans
Investment in company's common stock		$ 9	$ 24
U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		10,274	11,090	$ 11,210
U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		3,306	3,720
U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		5,422	5,952
U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,546	1,418
International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		4,109	4,244	$ 4,543
International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,196	1,014
International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		2,508	2,876
International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		405	354
U.S equity [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	1,699	2,087
U.S equity [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	1,699	2,087
U.S equity [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	0	0
U.S equity [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	0	0
U.S equity [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	392	241
U.S equity [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	382	241
U.S equity [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	10	0
U.S equity [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[1]	0	0
International Equity Securities [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,302	1,297
International Equity Securities [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,296	1,297
International Equity Securities [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		6	0
International Equity Securities [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
International Equity Securities [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		457	313
International Equity Securities [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		435	313
International Equity Securities [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		22	0
International Equity Securities [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Collective Trusts Mutual Funds Equity [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	2,460	3,240
Collective Trusts Mutual Funds Equity [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	18	22
Collective Trusts Mutual Funds Equity [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	2,442	3,218
Collective Trusts Mutual Funds Equity [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	0	0
Collective Trusts Mutual Funds Equity [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	572	979
Collective Trusts Mutual Funds Equity [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	7	173
Collective Trusts Mutual Funds Equity [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	565	806
Collective Trusts Mutual Funds Equity [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	0	0
Government [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		257	84
Government [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		46	47
Government [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		211	37
Government [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Government [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,089	1,066
Government [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		93	53
Government [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		996	1,013
Government [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Corporate [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,654	1,502
Corporate [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Corporate [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1,654	1,502
Corporate [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Corporate [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		615	585
Corporate [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		33	26
Corporate [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		557	537
Corporate [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		25	22
Bank Loans [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		148
Bank Loans [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Bank Loans [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		148
Bank Loans [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Bank Loans [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Bank Loans [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Bank Loans [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Bank Loans [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0
Mortgage-Backed Securities [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	1
Mortgage-Backed Securities [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Mortgage-Backed Securities [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	1
Mortgage-Backed Securities [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Mortgage-Backed Securities [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	1
Mortgage-Backed Securities [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Mortgage-Backed Securities [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	1
Mortgage-Backed Securities [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	0
Other Asset Backed [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		1	0
Other Asset Backed [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other Asset Backed [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Collective Trusts/Mutual Funds [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	933	1,174
Collective Trusts/Mutual Funds [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	0	0
Collective Trusts/Mutual Funds [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	933	1,174
Collective Trusts/Mutual Funds [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	0	0
Collective Trusts/Mutual Funds [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	269	394
Collective Trusts/Mutual Funds [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	12	16
Collective Trusts/Mutual Funds [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	257	378
Collective Trusts/Mutual Funds [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[2]	0	0
Mixed Funds [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	0	0
Mixed Funds [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	0	0
Mixed Funds [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	0	0
Mixed Funds [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	0	0
Mixed Funds [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	85	122
Mixed Funds [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	4	3
Mixed Funds [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	81	119
Mixed Funds [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[3]	0	0
Real Estate [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	1,494	1,364
Real Estate [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	0	0
Real Estate [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	0	0
Real Estate [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	1,494	1,364
Real Estate [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	378	329
Real Estate [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	0	0
Real Estate [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	0	0
Real Estate [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[4]	378	329
Cash And Cash Equivalents [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		253	270
Cash And Cash Equivalents [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		253	270
Cash And Cash Equivalents [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Cash And Cash Equivalents [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Cash And Cash Equivalents [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		232	190
Cash And Cash Equivalents [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		232	189
Cash And Cash Equivalents [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	1
Cash And Cash Equivalents [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets		0	0
Other [Member] | U.S. [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	72	71
Other [Member] | U.S. [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	(6)	(3)
Other [Member] | U.S. [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	26	20
Other [Member] | U.S. [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	52	54
Other [Member] | International [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	19	24
Other [Member] | International [Member] | Level 1 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	(2)	0
Other [Member] | International [Member] | Level 2 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	19	21
Other [Member] | International [Member] | Level 3 [Member]
Fair Value Measurements of Company's Pension Plans
Fair value of plan assets	[5]	$ 2	$ 3

[1] U.S. equities include investments in the company’s common stock in the amount of $9 at December 31, 2015, and $24 at December 31, 2014.

[2] Collective Trusts/Mutual Funds for U.S. plans are entirely index funds; for International plans, they are mostly index funds. For these index funds, the Level 2 designation is partially based on the restriction that advance notification of redemptions, typically two business days, is required.

[3] Mixed funds are composed of funds that invest in both equity and fixed-income instruments in order to diversify and lower risk.

[4] The year-end valuations of the U.S. real estate assets are based on internal appraisals by the real estate managers, which are updates of third-party appraisals that occur at least once a year for each property in the portfolio.

[5] The “Other” asset class includes net payables for securities purchased but not yet settled (Level 1); dividends and interest- and tax-related receivables (Level 2); insurance contracts and investments in private-equity limited partnerships (Level 3).