CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)		$ 17,587	$ (10,260)	$ 144,834	$ (124,364)
Postretirement benefits:
Net gain	[1]	(1,429)	0	(1,429)	0
Prior service credit	[2]	5,449	0	5,449	0
Amortization of prior service cost	[3]	(1,551)	17	(1,523)	52
Amortization of gain	[4]	287	0	0	0
Total other comprehensive income (loss)		2,756	17	2,497	52
Comprehensive income (loss)		$ 20,343	$ (10,243)	$ 147,331	$ (124,312)

[1] Net of income taxes of $837 for the three and nine months ended September 30, 2017.

[2] Net of income taxes of $(3,194) for the three months and nine months ended September 30, 2017.

[3] Net of income taxes of $909 and $(10) for the three months ended September 30, 2017 and 2016, respectively, and $893 and $(31) for the nine months ended September 30, 2017 and 2016, respectively.

[4] Net of income taxes of $(168) for the three months ended September 30, 2017.