Asset Retirement Obligations

12 Months Ended

Dec. 31, 2021

Asset Retirement Obligation Disclosure [Abstract]

Reconciliations of the Company’s asset retirement obligations are as follows:


	December 31,
	2021		2020
	(Dollars in millions)
Balance at beginning of period	$	728.2	$	752.3

Liabilities settled or disposed	(72.4)		(38.4)
Accretion expense	54.9		56.0
Revisions to estimates	9.1		(41.7)
Balance at end of period	$	719.8	$	728.2
Less: Current portion (included in “Accounts payable and accrued expenses”)	65.0		77.7
Noncurrent obligation (included in “Asset retirement obligations”)	$	654.8	$	650.5
Balance at end of period — active locations	$	511.8	$	471.8
Balance at end of period — closed or inactive locations	$	208.0	$	256.4

The credit-adjusted, risk-free interest rates utilized to estimate the Company’s asset retirement obligations ranged from 7.89% for life of mines 3 years or less to 10.12% for life of mines greater than 20 years for both U.S. and Australia reclamation obligations at December 31, 2021 and ranged from 9.16% for life of mines 3 years or less to 12.74% for life of mines greater than 20 years for both U.S. and Australia reclamation obligations at December 31, 2020.

As of December 31, 2021 and 2020, the Company had $1,294.7 million and $1,451.9 million, respectively, in surety bonds outstanding to secure reclamation obligations. Additionally, the Company had $323.0 million and $315.0 million, respectively, of letters of credit in support of reclamation obligations as of December 31, 2021 and 2020.