Financial risk management and financial instruments - Financing Risk (Details)	12 Months Ended
Jun. 30, 2020
Financial risk management and financial instruments
Target minimum average time to maturity for long-term borrowings	2 years

The entity's targeted minimum period for the average time to maturity of long-term borrowings.

No definition available.

Name:	ssl_LongTermBorrowingsTargetMinimumAverageTimeToMaturity
Namespace Prefix:	ssl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration