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

6 Months Ended

Jun. 30, 2013

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 June 30, 2013 are summarized below:

	Asset Retirement Obligation		Contractual Third-Party Reclamation Receivable		Reclamation Deposits
	(In thousands)
Rosebud	$	119,090	$	18,148	$	73,744
Jewett	74,833		74,833		—
Absaloka	27,078		406		—
Beulah	18,802		—		—
Kemmerer	17,491		—		—
Savage	4,997		—		—
ROVA	860		—		—
Total	$	263,151	$	93,387	$	73,744

Changes in Company's asset retirement obligations

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

	Six Months Ended June 30,
	2013			2012
	(In thousands)
Asset retirement obligations, beginning of year (including current portion)	$	263,847		$	247,478
Accretion	10,951			10,856
Liabilities settled	(11,647		)	(8,744		)
Changes due to amount and timing of reclamation	—			(4,757		)
ARO acquired	—			15,103
Asset retirement obligations, end of period	263,151			259,936
Less current portion	(24,105		)	(18,489		)
Asset retirement obligations, less current portion	$	239,046		$	241,447

Carrying value and estimated fair value of reclamation deposits

The Company’s carrying value and estimated fair value of its reclamation deposits at June 30, 2013 are as follows:

	Carrying Value		Fair Value		Fair Value Hierarchy
	(In thousands)
Cash and cash equivalents	$	46,245	$	46,245	Level 1
Held-to-maturity securities	12,194		12,932		Level 2
Time deposits	14,289		14,289		Level 1
Available-for-sale securities	1,016		1,016		Level 1
	$	73,744	$	74,482

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 June 30, 2013 are as follows (in thousands):

Amortized cost	$	12,194
Gross unrealized holding gains	811
Gross unrealized holding losses	(73		)
Fair value	$	12,932

Schedule of maturities of held-to-maturity investments

Maturities of held-to-maturity securities are as follows at June 30, 2013:

	Amortized Cost		Fair Value
	(In thousands)
Within one year	$	—	$	—
Due in five years or less	6,541		6,870
Due after five years to ten years	3,454		3,597
Due in more than ten years	2,199		2,465
	$	12,194	$	12,932

Cost basis, gross unrealized holding gains and fair value of available-for-sale securities

The cost basis, gross unrealized holding gains and fair value of available-for-sale securities at June 30, 2013 are as follows (in thousands):

Cost basis	$	1,000
Gross unrealized holding gains	16
Fair value	$	1,016