Bank overdrafts and short-term borrowings - Summary of Weighted Average Interest Rates on Bank Overdrafts and Short-Term Borrowings (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about borrowings [abstract]
Bank overdrafts	4.13%	4.35%
Borrowings	2.55%	2.69%

Weighted average interest rates on short-term borrowings.

No definition available.

Name:	ntz_WeightedAverageInterestRatesOnShorttermBorrowings
Namespace Prefix:	ntz_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration