Employee Benefits - Schedule of Fair Value of Other Plan Assets (Details) (Other [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	$ 1,161		$ 1,061		$ 1,009
Cash and cash equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	12		11
Global [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	295	[1]	318	[1]
Pooled funds - North America [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	42	[1]	52	[1]
Pooled funds - Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	629	[1]	509	[1]
Pooled funds - Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	18	[1]	20	[1]
Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	35	[2]	61	[2]
Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	74	[2]	14	[2]
Pooled funds - Commodities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	21	[1]	32	[1]
Pooled funds - REITS [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	3	[1]	5	[1]
Pooled funds - Real estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total			17	[1],[3]
Alternative investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	8	[1],[4]	8	[1],[4]
Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	24		14
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	12		11
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	12		11
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Global [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - North America [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[2]	0	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[2]	0	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - Commodities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - REITS [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled funds - Real estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total			0	[1],[3]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Alternative investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1],[4]	0	[1],[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0		0
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	1,141		1,025
Significant Other Observable Inputs (Level 2) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0		0
Significant Other Observable Inputs (Level 2) [Member] | Global [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	295	[1]	318	[1]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - North America [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	42	[1]	52	[1]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	629	[1]	509	[1]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	18	[1]	20	[1]
Significant Other Observable Inputs (Level 2) [Member] | Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	35	[2]	61	[2]
Significant Other Observable Inputs (Level 2) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	74	[2]	14	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - Commodities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	21	[1]	32	[1]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - REITS [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	3	[1]	5	[1]
Significant Other Observable Inputs (Level 2) [Member] | Pooled funds - Real estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total			0	[1],[3]
Significant Other Observable Inputs (Level 2) [Member] | Alternative investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1],[4]	0	[1],[4]
Significant Other Observable Inputs (Level 2) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	24		14
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	8		25		28
Significant Unobservable Inputs (Level 3) [Member] | Cash and cash equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Global [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - North America [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Fixed income securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[2]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - Commodities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - REITS [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Pooled funds - Real estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	0		17	[1],[3]	17
Significant Unobservable Inputs (Level 3) [Member] | Alternative investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	8	[1],[4]	8	[1],[4]	11
Significant Unobservable Inputs (Level 3) [Member] | Derivatives [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	$ 0		$ 0

[1] Consists of various equity, fixed income, commodity, and real estate mutual fund type investment vehicles.

[2] Consists of corporate and government bonds and fixed income derivatives.

[3] Consists of property funds and trusts holding direct real estate investments.

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