Provisions for employee benefits (Details 5)	Dec. 31, 2017	Dec. 31, 2016
TFR [Member]
Statement Line Items [Line Items]
Discount rate	1.50%	1.00%
Rate of compensation increase	2.50%	2.00%
Rate of price inflation	1.50%	1.00%
Foreign defined benefit plans [Member] \| Bottom Of Range [Member]
Statement Line Items [Line Items]
Discount rate	0.60%	0.60%
Rate of compensation increase	1.50%	1.00%
Rate of price inflation	0.60%	0.60%
Foreign defined benefit plans [Member] \| Top Of Range [Member]
Statement Line Items [Line Items]
Discount rate	15.50%	17.50%
Rate of compensation increase	13.50%	15.00%
Rate of price inflation	14.80%	13.50%
FISDE and other foreign medical plans [Member]
Statement Line Items [Line Items]
Discount rate	1.50%	1.00%
Rate of price inflation	1.50%	1.00%
Other benefit plans [Member] \| Bottom Of Range [Member]
Statement Line Items [Line Items]
Discount rate	0.00%	0.00%
Other benefit plans [Member] \| Top Of Range [Member]
Statement Line Items [Line Items]
Discount rate	1.50%	1.00%
Rate of price inflation	1.50%	1.00%

No definition available.

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- Definition

The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 144
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard
-URIDate 2017-03-09

+ Details

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- Definition

The expected rate of inflation that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

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- Definition

The expected rate of salary increases used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

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