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Asset Retirement Obligations (ARO) (Tables)

12 Months Ended

Dec. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

Reconciliation of Beginning and Ending Aggregate Carrying Amount of Asset Retirement Obligation

A reconciliation of the beginning and ending aggregate carrying amount of the ARO is shown in the following table.

						December 31,
(Millions of dollars)						2020						2019
Balance at beginning of period						$	32.8					$	30.7
Accretion expense						2.3						2.1
Settlement of liabilities						(0.8)						(0.4)
Liabilities incurred						0.8						0.4
Balance at end of period						$	35.1					$	32.8

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- References

No definition available.

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- Definition

Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859

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