Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (10,660)	$ 14,823
Other comprehensive income (loss):
Unrealized gain on derivatives (net of tax of $21and $2 for the three months ended March 31, 2016 and 2015, respectively)	35	3
Unrealized gain (loss) on investments (net of tax of $(3) and $22 for the three months ended March 31, 2016 and 2015, respectively)	(5)	35
Pension and other post-retirement benefits liability adjustment (net of tax of $(1,541) and $(235) for the three months ended March 31, 2016 and 2015, respectively)	(2,558)	(379)
Comprehensive income (loss)	$ (13,188)	$ 14,482