RESTRICTED INVESTMENTS AND BOND COLLATERAL (Tables)

12 Months Ended

Dec. 31, 2013

Disclosure Restricted Investments and Bond Collateral [Abstract]

Components of restricted investments and bond collateral

The Company’s restricted investments and bond collateral consist of the following:

	December 31,
	2013			2012
	(In thousands)
Coal Segment:
WML debt reserve account	$	13,067		$	13,062
Reclamation bond collateral:
Kemmerer Mine	24,966			24,702
Absaloka Mine	11,653			14,507
Rosebud Mine	3,145			12,495
Beulah Mine	1,270			1,270
Power Segment:
Letter of credit account	5,998			5,990
Corporate Segment:
Postretirement medical benefit bonds	8,467			8,593
Workers’ compensation bonds	6,667			6,590
Total restricted investments and bond collateral	75,233			87,209
Less current portion	(5,998		)	—
Total restricted investments and bond collateral, less current portion	$	69,235		$	87,209

Carrying value and estimated fair value of restricted investments and bond collateral

The Company’s carrying value and estimated fair value of its restricted investments and bond collateral at December 31, 2013 are as follows:

	Carrying Value		Fair Value
	(In thousands)
Cash and cash equivalents	$	40,605	$	40,605
Time deposits	2,444		2,444
Held-to-maturity securities	32,184		32,046
	$	75,233	$	75,095

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 are as follows:

	December 31,
	2013			2012
	(In thousands)
Amortized cost	$	32,184		$	3,983
Gross unrealized holding gains	309			356
Gross unrealized holding losses	(447		)	—
Fair value	$	32,046		$	4,339

The amortized cost, gross unrealized holding gains and losses and fair value of held-to-maturity securities are as follows:

	Years Ended December 31,
	2013			2012
	(In thousands)
Amortized cost	$	11,396		$	19,832
Gross unrealized holding gains	764			1,190
Gross unrealized holding losses	(74		)	(9		)
Fair value	$	12,086		$	21,013

Maturities of held-to-maturity securities

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

	Amortized Cost		Fair Value
	(In thousands)
Due within one year	$	1,111	$	1,143
Due in five years or less	17,839		17,944
Due after five years to ten years	6,769		6,665
Due in more than ten years	6,465		6,294
	$	32,184	$	32,046

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

	Amortized Cost		Fair Value
	(In thousands)
Within one year	$	17	$	17
Due in five years or less	6,645		6,976
Due after five years to ten years	3,002		3,123
Due in more than ten years	1,732		1,970
	$	11,396	$	12,086

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 are as follows:

	December 31,
	2013		2012
	(In thousands)
Cost basis	$	—	$	175
Gross unrealized holding gains	—		16
Fair value	$	—	$	191