Asset Retirement Obligations

12 Months Ended

Dec. 31, 2019

Asset Retirement Obligation Disclosure [Abstract]

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



	December 31,
	2019			2018
	(Dollars in millions)
Balance at beginning of period	$	750.2		$	691.1
Liabilities incurred or acquired	—			16.3
Liabilities settled or disposed	(47.7		)	(57.8		)
Accretion expense	54.1			48.5
Revisions to estimates	(4.3		)	52.1
Balance at end of period	$	752.3		$	750.2
Less: Current portion (included in “Accounts payable and accrued expenses”)	98.2			63.8
Noncurrent obligation (included in “Asset retirement obligations”)	$	654.1		$	686.4
Balance at end of period — active locations	$	525.4		$	671.8
Balance at end of period — closed or inactive locations	$	226.9		$	78.4

During the year ended December 31, 2018, the Company acquired the Shoal Creek Mine and the related asset retirement obligations, as further discussed in Note 3. “Acquisition of Shoal Creek Mine.” The changes in mine operations impacted reclamation estimates and are reflected in the asset retirement obligation asset and liability as of December 31, 2019 and 2018, respectively.

The credit-adjusted, risk-free interest rates utilized to estimate the Company’s asset retirement obligations 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 and ranged from 7.61% for life of mines 3 years or less to 11.54% for life of mines greater than 20 years for both U.S. and Australia reclamation obligations at December 31, 2018.

As of December 31, 2019 and 2018, the Company had $1,401.7 million and $1,317.0 million, respectively, in surety bonds and bank guarantees outstanding to secure reclamation obligations. Additionally, the Company had $106.1 million and $142.3 million, respectively, of letters of credit in support of reclamation obligations as of December 31, 2019 and 2018.