Asset Retirement Obligations

12 Months Ended

Dec. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

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


	December 31,
	2020		2019
	(Dollars in millions)
Balance at beginning of period	$	752.3	$	750.2

Liabilities settled or disposed	(38.4)		(47.7)
Accretion expense	56.0		54.1
Revisions to estimates	(41.7)		(4.3)
Balance at end of period	$	728.2	$	752.3
Less: Current portion (included in “Accounts payable and accrued expenses”)	77.7		98.2
Noncurrent obligation (included in “Asset retirement obligations”)	$	650.5	$	654.1
Balance at end of period — active locations	$	471.8	$	525.4
Balance at end of period — closed or inactive locations	$	256.4	$	226.9

The credit-adjusted, risk-free interest rates utilized to estimate the Company’s asset retirement obligations 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 and ranged from 9.24% for life of mines 3 years or less to 12.38% for life of mines greater than 20 years for both U.S. and Australia reclamation obligations at December 31, 2019.As of December 31, 2020 and 2019, the Company had $1,451.9 million and $1,401.7 million, respectively, in surety bonds outstanding to secure reclamation obligations. Additionally, the Company had $315.0 million and $106.1 million, respectively, of letters of credit in support of reclamation obligations as of December 31, 2020 and 2019.