For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of contributions made by the employer to defined benefit plans.

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Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period.

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The amount of the cost recognized during the period for defined contribution plans.

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Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Oct. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay (up to)	4.00%
Maximum annual contributions per employee, percent	7.00%
Contributions by employer		$ 56
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in current fiscal year		200
Unites States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		$ 54	$ 40
Unites States \| Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation U.S. Plan		64.00%
Actual asset allocation percentage of equity		64.00%
Unites States \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation U.S. Plan		36.00%
Actual asset allocation percentage of equity		36.00%
United Kingdom \| Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation U.S. Plan		48.00%
Actual asset allocation percentage of equity		47.00%
United Kingdom \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation U.S. Plan		52.00%
Actual asset allocation percentage of equity		53.00%
United Kingdom \| Geographic Concentration Risk \| Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Concentration risk percentage		81.00%