Line of Credit Facility, Increased Maximum Borrowing Capacity

No definition available.

Name:	nxt_LineOfCreditFacilityIncreasedMaximumBorrowingCapacity
Namespace Prefix:	nxt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

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Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Credit facilities (Details) - USD ($) $ in Millions	Sep. 08, 2025	Dec. 31, 2025
Credit Facility \| Minimum
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	0.075%
Credit Facility \| Maximum
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	0.20%
Letter of Credit \| Minimum
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	0.875%
Letter of Credit \| Maximum
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	1.50%
Revolving Credit Facility \| New Credit Agreement \| Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing, capacity	$ 1,000.0
Line of credit facility, increased maximum borrowing capacity	250.0
Unamortized debt issuance expense		$ 2.0
Line of credit facility, remaining borrowing capacity		891.4
Revolving Credit Facility \| New Credit Agreement \| Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing, capacity		500.0
Letter of Credit \| New Credit Agreement \| Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing, capacity	500.0
Line of credit facility, remaining borrowing capacity		$ 108.6
Bridge Loan \| New Credit Agreement \| Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing, capacity	150.0
Existing Credit Agreement \| New Credit Agreement \| Line of Credit
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt	$ (5.8)