Long-term debt - Borrowings redemption prices (Details) - Senior unsecured notes - due July 15, 2027	12 Months Ended
Dec. 31, 2024
July 15, 2024
Long Term Debt [Line Items]
Borrowings redemption price percentage	101.88%
July 15, 2025 and thereafter
Long Term Debt [Line Items]
Borrowings redemption price percentage	100.00%

The percentage rate of the aggregate principle amount that determines the redemption price of borrowings.

No definition available.

Name:	ngd_BorrowingsRedemptionPricePercentage
Namespace Prefix:	ngd_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration