Pension and Other Postretirement Employee Benefit Plans - Defined Benefit Pension Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, benefit obligation expense retirement plan	$ 237,000,000	$ 257,000,000
Defined contribution plans
Employer matching percent of employees' gross pay	5.00%
Employee annual compensation amount not eligible for employers matching contributions	$ 250,000
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Period after which employees begin to accrue plan benefits	1 year
Period after which benefits generally vest	3 years
Defined contribution plans
Period after which employees begin to receive matching contributions	1 year
Period after which matching contributions vest for employees hired after May 1, 2009	3 years
Funded status of plan - supplemental information
Unfunded postretirement benefit obligation, U.K. Plan	$ 32,000,000	37,000,000
Defined benefit pension plans, U.S.
Change in benefit obligation
Benefit obligation, beginning of year	(12,536,000,000)	(10,776,000,000)
Benefits earned during the year	(340,000,000)	(281,000,000)	$ (314,000,000)
Interest cost on benefit obligations	(498,000,000)	(534,000,000)	(447,000,000)
Plan amendments	0	(53,000,000)
Special termination benefits	0	0
Curtailments	0	0
Net gain/(loss)	702,000,000	(1,669,000,000)
Benefits paid	760,000,000	777,000,000
Foreign exchange impact and other	0	0
Benefit obligation, end of year	(11,912,000,000)	(12,536,000,000)	(10,776,000,000)
Change in plan assets
Fair value of plan assets, beginning of year	14,623,000,000	14,354,000,000
Actual return on plan assets	231,000,000	1,010,000,000
Firm contributions	31,000,000	36,000,000
Employee contributions	0	0
Benefits paid	(760,000,000)	(777,000,000)
Foreign exchange impact and other	0	0
Fair value of plan assets, end of year	14,125,000,000	14,623,000,000	14,354,000,000
Net funded status	2,213,000,000	2,087,000,000
Accumulated benefit obligation, end of year	(11,774,000,000)	(12,375,000,000)
Defined benefit pension plans, U.S. | Participation rights under participating annuity contracts
Change in plan assets
Fair value of plan assets, beginning of year	336,000,000
Fair value of plan assets, end of year	533,000,000	336,000,000
Defined benefit pension plans, U.S. | Accrued receivables
Funded status of plan - supplemental information
Defined benefit plans, amounts not measured at fair value	74,000,000	106,000,000
Defined benefit pension plans, U.S. | Accrued liabilities
Funded status of plan - supplemental information
Defined benefit plans, amounts not measured at fair value	123,000,000	257,000,000
Non-U.S. defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, estimated future employer contributions in next fiscal year	47,000,000
Defined benefit plan, contractually required future employer contributions in next fiscal year	31,000,000
Change in benefit obligation
Benefit obligation, beginning of year	(3,640,000,000)	(3,433,000,000)
Benefits earned during the year	(37,000,000)	(33,000,000)	(34,000,000)
Interest cost on benefit obligations	(112,000,000)	(137,000,000)	(125,000,000)
Plan amendments	0	0
Special termination benefits	(1,000,000)	(1,000,000)
Curtailments	0	0
Employee contributions	(7,000,000)	(7,000,000)
Net gain/(loss)	146,000,000	(408,000,000)
Benefits paid	120,000,000	119,000,000
Foreign exchange impact and other	184,000,000	260,000,000
Benefit obligation, end of year	(3,347,000,000)	(3,640,000,000)	(3,433,000,000)
Change in plan assets
Fair value of plan assets, beginning of year	3,718,000,000	3,532,000,000
Actual return on plan assets	52,000,000	518,000,000
Firm contributions	45,000,000	46,000,000
Employee contributions	7,000,000	7,000,000
Benefits paid	(120,000,000)	(119,000,000)
Foreign exchange impact and other	(191,000,000)	(266,000,000)
Fair value of plan assets, end of year	3,511,000,000	3,718,000,000	3,532,000,000
Net funded status	164,000,000	78,000,000
Accumulated benefit obligation, end of year	(3,322,000,000)	(3,615,000,000)
OPEB plans
Change in benefit obligation
Benefit obligation, beginning of year	(842,000,000)	(826,000,000)
Benefits earned during the year	(1,000,000)	0	(1,000,000)
Interest cost on benefit obligations	(31,000,000)	(38,000,000)	(35,000,000)
Plan amendments	0	0
Special termination benefits	0	0
Curtailments	0	(3,000,000)
Employee contributions	(25,000,000)	(62,000,000)
Net gain/(loss)	71,000,000	(58,000,000)
Benefits paid	88,000,000	145,000,000
Expected Medicare Part D subsidy receipts	(6,000,000)	(2,000,000)
Foreign exchange impact and other	2,000,000	2,000,000
Benefit obligation, end of year	(744,000,000)	(842,000,000)	(826,000,000)
Change in plan assets
Fair value of plan assets, beginning of year	1,903,000,000	1,757,000,000
Actual return on plan assets	13,000,000	159,000,000
Firm contributions	2,000,000	3,000,000
Employee contributions	0	0
Benefits paid	(63,000,000)	(16,000,000)
Foreign exchange impact and other	0	0
Fair value of plan assets, end of year	1,855,000,000	1,903,000,000	$ 1,757,000,000
Net funded status	1,111,000,000	1,061,000,000
OPEB plans | Overfunded plans
Change in plan assets
Net funded status	4,100,000,000	3,900,000,000
OPEB plans | Underfunded plans
Change in plan assets
Net funded status	$ 636,000,000	$ 708,000,000