Equity and Noncontrolling Interest - Additional Information (Details)		3 Months Ended	12 Months Ended
	Aug. 31, 2025	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2025 USD ($) $ / shares shares
Class of Stock [Line Items]
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, par value \| $ / shares		$ 0.0001	$ 0.0001
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Description of redemption			Cardinal’s ("OpCo's") amended and restated operating agreement provides that the Continuing Equity Holders have the right (the “Redemption Right”) to cause OpCo to redeem all or a portion of their Class B LLC Units, together with a corresponding number of shares of Class B Common Stock, for newly issued shares of Cardinal Infrastructure Group Inc.'s Class A Common Stock on a one-for-one basis (subject to customary adjustments for stock splits, stock dividends, and reclassifications). Alternatively, Cardinal Infrastructure Group Inc. may, at its option (the “Call Right”), elect to directly acquire the tendered LLC Units and Class B Common Stock from the Continuing Equity Holder in exchange for Class A Common Stock on the same one-for-one basis.
Gain or loss on exchange of equity transaction \| $			$ 0
Gain or loss recognized \| $		$ 0
OpCo
Class of Stock [Line Items]
Percentage of voting rights		100.00%	100.00%
Cardinal NC \| Aviator Paving Company LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	60.00%
Cardinal NC \| Cardinal Civil Contracting NC LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	70.00%
Cardinal NC \| Civil Drilling & Blasting, LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	90.00%
Cardinal NC \| Cardinal Civil Contracting Charlotte, LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	75.00%
Cardinal NC \| Cardinal Civil Contracting Triad, LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	80.00%
Cardinal NC \| Civil Underground and Boring Company, LLC
Class of Stock [Line Items]
Ownership interests in subsidiary	70.00%
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized		500,000,000	500,000,000
Common stock, par value per share \| $ / shares		$ 0.0001	$ 0.0001
Common stock voting rights			Each share of Class A Common Stock entitles its holder to one vote per share on all matters presented to Cardinal Infrastructure Group Inc.’s stockholders.
Common stock, shares issued		14,947,318	14,947,318
Common stock, shares outstanding		14,947,318	14,947,318
Class A Common Stock \| OpCo \| Continuing Equity Holders
Class of Stock [Line Items]
Stock split ratio			1
Class A Common Stock \| OpCo \| Cardinal Infrastructure Group Inc.
Class of Stock [Line Items]
Stock split ratio			1
Class B Common Stock
Class of Stock [Line Items]
Common stock, shares authorized		500,000,000	500,000,000
Common stock, par value per share \| $ / shares		$ 0.0001	$ 0.0001
Common stock voting rights			Each share of Class B Common Stock entitles its holder to one vote per share on all matters presented to Cardinal Infrastructure Group Inc.’s stockholders.
Common stock, shares issued		23,387,813	23,387,813
Common stock, shares outstanding		23,387,813	23,387,813

Cardinal Infrastructure Group Inc. 10-K