ASSET RETIREMENT OBLIGATIONS, CONTRACTUAL THIRD-PARTY RECLAMATION RECEIVABLES, AND RECLAMATION DEPOSITS (Tables)

3 Months Ended

Mar. 31, 2014

Asset Retirement Obligation Disclosure [Abstract]

Summary of asset retirement obligations, contractual third-party reclamation receivables and reclamation deposits

The asset retirement obligation, contractual third-party reclamation receivable, and reclamation deposits for each of the Company’s mines and ROVA at March 31, 2014 are summarized below:

	Asset Retirement Obligation		Contractual Third-Party Reclamation Receivable		Reclamation Deposits
	(In thousands)
Rosebud	$	127,989	$	21,656	$	75,315
Jewett	74,247		74,247		—
Absaloka	37,286		346		—
Beulah	17,764		—		—
Kemmerer	17,569		—		—
Savage	5,499		—		—
ROVA	909		—		—
Total	$	281,263	$	96,249	$	75,315

Changes in Company's asset retirement obligations

Changes in the Company’s asset retirement obligations were as follows:

	Three Months Ended March 31,
	2014			2013
	(In thousands)
Asset retirement obligations, beginning of year (including current portion)	$	279,864		$	263,847
Accretion	5,836			5,481
Liabilities settled	(4,437		)	(5,839		)
Asset retirement obligations, end of period	281,263			263,489
Less current portion	(22,227		)	(23,154		)
Asset retirement obligations, less current portion	$	259,036		$	240,335

Carrying value and estimated fair value of reclamation deposits

The Company’s carrying value and estimated fair value of its reclamation deposits at March 31, 2014 are as follows:

	Carrying Value		Fair Value		Fair Value Hierarchy
	(In thousands)
Cash and cash equivalents	$	49,627	$	49,627	Level 1
Held-to-maturity securities	25,688		26,401		Level 2
	$	75,315	$	76,028

Amortized cost, gross unrealized holding gains and losses and fair value of held-to-maturity securities

The amortized cost, gross unrealized holding gains and losses and fair value of held-to-maturity securities at March 31, 2014 are as follows (in thousands):

Amortized cost	$	25,688
Gross unrealized holding gains	826
Gross unrealized holding losses	(113		)
Fair value	$	26,401

Reclamation Deposits [Member]

Schedule of Held-to-maturity Securities [Line Items]

Schedule of maturities of held-to-maturity investments

Maturities of held-to-maturity securities are as follows at March 31, 2014:

	Amortized Cost		Fair Value
	(In thousands)
Within one year	$	479	$	468
Due in five years or less	17,562		17,880
Due after five years to ten years	4,869		5,023
Due in more than ten years	2,778		3,030
	$	25,688	$	26,401