Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ (107,241)	$ 1,106	$ 1,100
Other comprehensive income (loss):
Unrealized holding gain on investments arising during period			64
Retirement plan gain (loss)	24,257	(9,437)	(8,863)
Income tax benefit (provision) on other comprehensive income (loss)	(5,003)	3,607	3,358
Other comprehensive income (loss), net of tax	19,254	(5,830)	(5,441)
Comprehensive loss	$ (87,987)	$ (4,724)	$ (4,341)