Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 33,403	$ (203,116)
Pension and postretirement plans:
Amortization of prior service cost, net of tax of ($43) and ($47), respectively	(71)	(78)
Amortization of net loss, including settlement charges, net of tax of $1 and $1,168, respectively	2	1,890
Current period change in fair value of pension and postretirement plans, net of tax of ($6) in 2016	0	(9)
Total pension and postretirement plans	(69)	1,803
Comprehensive Income (Loss)	$ 33,334	$ (201,313)