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

3 Months Ended

Mar. 31, 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 March 31, 2013 are summarized below:

	Asset Retirement Obligation		Contractual Third-Party Reclamation Receivable		Reclamation Deposits
	(In thousands)
Rosebud	$	118,441	$	17,808	$	73,100
Jewett	76,426		76,426		—
Absaloka	26,439		395		—
Beulah	18,441		—		—
Kemmerer	18,006		—		—
Savage	4,891		—		—
ROVA	845		—		—
Total	$	263,489	$	94,629	$	73,100

Changes in Company's asset retirement obligations

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

	Three Months Ended March 31,
	2013			2012
	(In thousands)
Asset retirement obligations, beginning of year (including current portion)	$	263,847		$	247,478
Accretion	5,481			5,283
Liabilities settled	(5,839		)	(4,411		)
Changes due to amount and timing of reclamation	—			(4,757		)
ARO acquired	—			15,103
Asset retirement obligations, end of period	263,489			258,696
Less current portion	(23,154		)	(16,050		)
Asset retirement obligations, less current portion	$	240,335		$	242,646

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, 2013 are as follows:

	Carrying Value		Fair Value		Fair Value Hierarchy
	(In thousands)
Cash and cash equivalents	$	44,022	$	44,022	Level 1
Held-to-maturity securities	13,750		14,830		Level 2
Time deposits	14,289		14,289		Level 1
Available-for-sale securities	1,039		1,039		Level 1
	$	73,100	$	74,180

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, 2013 are as follows (in thousands):

Amortized cost	$	13,750
Gross unrealized holding gains	1,082
Gross unrealized holding losses	(2		)
Fair value	$	14,830

Schedule of maturities of held-to-maturity investments

Maturities of held-to-maturity securities are as follows at March 31, 2013:

	Amortized Cost		Fair Value
	(In thousands)
Within one year	$	1,001	$	1,005
Due in five years or less	6,027		6,477
Due after five years to ten years	4,191		4,508
Due in more than ten years	2,531		2,840
	$	13,750	$	14,830

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 March 31, 2013 are as follows (in thousands):

Cost basis	$	1,000
Gross unrealized holding gains	39
Fair value	$	1,039