26. Operating revenue (Details 1) - BRL (R$) R$ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenue Details 1
Sanitation services	R$ 12,223,746	R$ 11,122,232	R$ 8,946,825
Construction revenue	3,150,877	3,732,877	3,336,716
Sales Tax	(757,619)	(756,901)	(571,972)
Regulation, Control and Oversight Fee (TRCF)	(8,771)	0	0
Net operating revenue	R$ 14,608,233	R$ 14,098,208	R$ 11,711,569

The income arising in the course of an entity's ordinary activities. Income is increases in economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in an increase in equity, other than those relating to contributions from equity participants.

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+ Details