Accumulated Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2018

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following items are included in accumulated other comprehensive income ("AOCI"):

				Pension,
				Postretirement
				and Other					Accumulated
				Post-					Other
	Derivative			Employment		Available-for-			Comprehensive
	Instruments			Benefits		Sale Securities			Income
	(In thousands)
Balance at December 31, 2017	$	647		$	19,720	$	—		$	20,367
Unrealized gains (losses)	6,697			—		(658		)	6,039
Amounts reclassified from AOCI	(140		)	—		—			(140		)
Balance at March 31, 2018	$	7,204		$	19,720	$	(658	)	$	26,266

Schedule of Comprehensive Income Reclassifications

The following amounts were reclassified out of AOCI:

	Three Months Ended March 31,
Details About AOCI Components	2018		2017		Line Item in the Condensed Consolidated Statement of Operations
(In thousands)
Coal hedges	$	—	$	—	Revenues
Interest rate hedges	140		—		Interest expense
	—		—		Provision for (benefit from) income taxes
	$	140	$	—	Net of tax
Pension, postretirement and other post-employment benefits
Amortization of prior service credits	$	—	$	—
Amortization of actuarial gains (losses), net	—		—
	—		—
	—		—		Provision for (benefit from) income taxes
	$	—	$	—	Net of tax
Available-for-sale securities	$	—	$	332	Interest and investment income
	—		—		Provision for (benefit from) income taxes
	$	—	$	332	Net of tax