Pension and Other Benefit Plans - Narrative (Details)					12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 06, 2014 USD ($)	Dec. 20, 2013 USD ($)	Apr. 01, 2016 USD ($) number_of_plans shares		Apr. 03, 2015 USD ($)		Mar. 28, 2014 USD ($)	Nov. 27, 2015 USD ($)	Jul. 31, 2014 USD ($)	Mar. 29, 2013
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets					$ 0		$ 1,479,000,000	[1]
Current liabilities of discontinued operations					0		691,000,000	[1]
Noncurrent liabilities					$ 0		754,000,000	[1]
Funded percentage (in hundredths)			74.00%
Increase (decrease) in PBO											$ (3,000,000)
Number of deferred compensation plans | number_of_plans					2
Deferred compensation plan, liability					$ 74,000,000		117,000,000
Deferred compensation plan, expense					$ 3,000,000		$ 2,000,000		$ 9,000,000
Duration of Aon Hewitt AA Only Above Median Curve					100 years
Nearest amount discount rates yield curve rounded to							0.10%
Defined contribution plan contribution					$ 132,000,000		$ 177,000,000		$ 179,000,000
Shares of company common stock held in defined contribution plan assets | shares					5,675,165
Key executives
Defined Benefit Plan Disclosure [Line Items]
Number of deferred compensation plans | number_of_plans					1
Non-employee directors
Defined Benefit Plan Disclosure [Line Items]
Number of deferred compensation plans | number_of_plans					1
Maximum deferral percentage					100.00%
Non-US pension plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets					$ 2,574,000,000		2,802,000,000
Non-US pension plans | Alternative Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets					539,000,000	[2]	$ 169,000,000	[3]
Non-US pension plans | SWITZERLAND
Defined Benefit Plan Disclosure [Line Items]
Gain (loss) on plan amendments	$ 7,000,000	$ (29,000,000)
Actuarial gain (loss)	7,000,000	(26,000,000)
Settlement gain (loss)	$ 0	$ (3,000,000)
Discount rate (in hundredths)	0.81%	1.20%					1.20%		2.10%
Economic benefit of lump sum payments	$ 14,000,000	$ 38,000,000
Funded percentage (in hundredths)	74.00%	78.00%
Expected long-term rates of return on assets	4.15%	3.60%
US pension plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension expense (income)					0		$ 3,000,000		$ (2,000,000)
UK pension plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate (in hundredths)				4.65%								4.31%
Funded percentage (in hundredths)				108.00%
Settlement gain (loss)				$ 443,000,000
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Contractual termination benefits					6,000,000		3,000,000		$ 17,000,000
Estimated future amortization of transitional obligation					1,000,000
Estimated future amortization of prior service credit					$ (9,000,000)
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)							$ (1,000,000)
Discount rate (in hundredths)			4.01%						4.32%
Reduction in PBO due to plan amendment			$ (99,000,000)
Expected return on assets (in hundredths)			7.50%
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate (in hundredths)					4.10%		3.70%
Accumulated benefit obligation					$ 25,000,000		$ 26,000,000
Fair value of plan assets							0
US pension plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					55.00%
US pension plans | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					35.00%
US pension plans | Alternative Investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					10.00%
US pension plans | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Gain (loss) on plan amendments					$ 0		0
Actuarial gain (loss)					$ (1,000,000)		$ 4,000,000
Discount rate (in hundredths)					3.90%		3.80%
Expected long-term rates of return on assets					7.90%		7.60%		7.20%
Increase (decrease) in PBO					$ 0		$ (3,000,000)
Accumulated benefit obligation					28,000,000		30,000,000
Fair value of plan assets					$ 23,000,000		$ 26,000,000		$ 29,000,000
Non-US pension plans
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations							32.00%
Non-US pension plans | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					35.00%
Non-US pension plans | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					33.00%
Non-US pension plans | Corporate Credit
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					23.00%
Non-US pension plans | Liability Driven Investment Products
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations					10.00%
Non-US pension plans | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain resulting from remeasurement					$ (126,000,000)		$ (274,000,000)		$ 101,000,000
Gain (loss) on plan amendments					(3,000,000)		1,000,000
Actuarial gain (loss)					$ (91,000,000)		$ 491,000,000
Discount rate (in hundredths)					3.10%		3.00%
Expected long-term rates of return on assets					6.30%		6.50%		6.20%
Increase (decrease) in PBO					$ (14,000,000)		$ (25,000,000)
Contractual termination benefits					6,000,000		3,000,000		$ 17,000,000
Accumulated benefit obligation					2,782,000,000		2,948,000,000
Fair value of plan assets					2,573,000,000		2,802,000,000		2,824,000,000
Net periodic pension expense (income)					60,000,000		$ 228,000,000		$ (105,000,000)
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | CSRA | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets										$ 3,000,000
Current liabilities of discontinued operations										9,000,000
Noncurrent liabilities										473,000,000
Accumulated other comprehensive income										$ 51,000,000
Actuarial gain resulting from remeasurement					20,000,000
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | CSRA | Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain resulting from remeasurement					$ 1,000,000
Minimum | US pension plans
Defined Benefit Plan Disclosure [Line Items]
Target allocations for cash and cash equivalents					0.00%
Maximum | US pension plans
Defined Benefit Plan Disclosure [Line Items]
Target allocations for cash and cash equivalents					10.00%

[1] Certain prior year balances were adjusted to give effect to discontinued operations as described in Note 4, for certain errors in previously issued financial statements related to income taxes as described in Note 1, and for the retrospective application of ASU 2015-17 and ASU 2016-09 as described in Note 1.

[2] Represents real estate, and other commingled funds consisting mainly of equities, bonds, or commodities.

[3] Represents real estate, and other commingled funds consisting mainly of equities, bonds, or commodities.