Employee Benefits - Schedule of Fair Value of U.S Plan Assets (Details) (U.S. Pension Plan [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Total	$ 2,036		$ 1,855		$ 1,631
Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	68	[1]	53	[1]
Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	329	[2]	303	[2]
Small cap domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	85	[2]	66	[2]
Large cap international [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	258	[2]	212	[2]
Equity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	285	[2]	361	[2]
Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	503	[3]	395	[3]
Government and agency bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	109	[3]	96	[3]
Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	20	[3]	25	[3]
Fixed income derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	49	[3]	13	[3]
Alternative investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	272	[4]	266	[4]
Commodity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	(8)	[5]	14	[5]
Real estate and REITS [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	66	[6]	51	[6]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	837		624
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	68	[1]	53	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	329	[2]	303	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Small cap domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	22	[2]	5	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Large cap international [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	114	[2]	66	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	209	[2]	146	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government and agency bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	29	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed income derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Alternative investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[4]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commodity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[5]	0	[5]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Real estate and REITS [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	66	[6]	51	[6]
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	575		965
Significant Other Observable Inputs (Level 2) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		[1]	0	[1]
Significant Other Observable Inputs (Level 2) [Member] | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	[2]	0	[2]
Significant Other Observable Inputs (Level 2) [Member] | Small cap domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	63	[2]	61	[2]
Significant Other Observable Inputs (Level 2) [Member] | Large cap international [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	144	[2]	146	[2]
Significant Other Observable Inputs (Level 2) [Member] | Equity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	76	[2]	215	[2]
Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	151	[3]	395	[3]
Significant Other Observable Inputs (Level 2) [Member] | Government and agency bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	80	[3]	96	[3]
Significant Other Observable Inputs (Level 2) [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	20	[3]	25	[3]
Significant Other Observable Inputs (Level 2) [Member] | Fixed income derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	49	[3]	13	[3]
Significant Other Observable Inputs (Level 2) [Member] | Alternative investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[4]	0	[4]
Significant Other Observable Inputs (Level 2) [Member] | Commodity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	(8)	[5]	14	[5]
Significant Other Observable Inputs (Level 2) [Member] | Real estate and REITS [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[6]	0	[6]
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	624		266		262
Significant Unobservable Inputs (Level 3) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Small cap domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Large cap international [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Equity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	352	[3]	0	[3]
Significant Unobservable Inputs (Level 3) [Member] | Government and agency bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[3]	0	[3]
Significant Unobservable Inputs (Level 3) [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[3]	0	[3]
Significant Unobservable Inputs (Level 3) [Member] | Fixed income derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[3]	0	[3]
Significant Unobservable Inputs (Level 3) [Member] | Alternative investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	272	[4]	266	[4]
Significant Unobservable Inputs (Level 3) [Member] | Commodity derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	[5]	0	[5]
Significant Unobservable Inputs (Level 3) [Member] | Real estate and REITS [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0	[6]	$ 0	[6]

[1] Consists of cash and institutional short-term investment funds.

[2] Consists of equity securities, equity derivatives, and pooled equity funds.

[3] Consists of corporate and government bonds, asset-backed securities, and fixed income derivatives.

[4] Consists of limited partnerships, private equity and hedge funds.

[5] Consists of long-dated options on a commodity index.

[6] Consists of exchange traded REITS.