Material accounting policies - Stock-based compensation and retention securities (Details)	12 Months Ended
Dec. 31, 2025
Material accounting policies
Expiration term of options	10 years

The maximum term of options granted under a share-based payment arrangement during the period.

No definition available.

Name:	ngen_MaximumTermOfOptionsGrantedForShareBasedPaymentArrangement
Namespace Prefix:	ngen_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration