Post-retirement benefit obligations - Sensitivity Analysis (Details) - Healthcare - ZAR (R) R in Millions	Jun. 30, 2018	Jun. 30, 2017
Sensitivity analysis
Cost inflation as premium over CPI	2.00%
South Africa \| Healthcare cost inflation
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%
Increase (decrease) in net obligation due to increase in actuarial assumption	R 582	R 594
Increase (decrease) in net obligation due to decrease in actuarial assumption	R (475)	R (487)
South Africa \| Discount rate
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%
Increase (decrease) in net obligation due to increase in actuarial assumption	R (452)	R (472)
Increase (decrease) in net obligation due to decrease in actuarial assumption	R 562	R 584
South Africa \| Pension increase
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%
Increase (decrease) in net obligation due to increase in actuarial assumption	R 159	R 145
Increase (decrease) in net obligation due to decrease in actuarial assumption	R (191)	R (183)
United States of America \| Healthcare cost inflation
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%
United States of America \| Discount rate
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%
Increase (decrease) in net obligation due to increase in actuarial assumption	R (21)	R (20)
Increase (decrease) in net obligation due to decrease in actuarial assumption	R 25	R 24
United States of America \| Pension increase
Sensitivity analysis
Increase in actuarial assumption (as a percent)	1.00%	1.00%
Decrease in actuarial assumption (as a percent)	1.00%	1.00%

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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by a decrease in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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-Paragraph 145
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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by an increase in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

+ Details

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- Definition

The reasonably possible percentage of the decrease in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

+ Details

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The reasonably possible percentage of the increase in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

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- Definition

The percentage of healthcare cost inflation is CPI inflation over the long term.

+ References

No definition available.

+ Details

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