Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2025

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

	December 31,
(Millions of dollars)	2025		2024
Goodwill	$	328.0	$	328.0

Schedule of Intangible Assets

Intangible assets subject to amortization at December 31, 2025 and 2024 consisted of the following:

	Remaining Useful Life (in years)	December 31, 2025				December 31, 2024
(Millions of dollars)		Cost		Net		Cost		Net
Intangible assets subject to amortization:
Pipeline space	29.7	$	39.6	$	29.7	$	39.6	$	30.7
Intangible lease liability	8.6	(9.1)		(5.8)		(9.1)		(6.6)
Total intangible assets subject to amortization		30.5		23.9		30.5		24.1
Intangible assets not subject to amortization, indefinite lives:
Trade name		115.4		115.4		115.4		115.4
Intangible assets, net of amortization		$	145.9	$	139.3	$	145.9	$	139.5