Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income (loss)	$ 82,986	$ (149,226)	$ (132,988)	$ (696,029)
Net unrealized gain on derivative instruments qualifying as hedges:
Reclassification adjustment for loss on derivative instruments included in net income (loss), net of tax of $56 and $60 for the three months ended and $170 and $181 for the nine months ended in 2016 and 2015, respectively	92	100	275	299
Postretirement liability adjustment:
Amortization of postretirement liability (gains) losses included in net periodic benefit cost, net of tax of $143 and $233 for the three months ended and $(676) and $881 for the nine months ended in 2016 and 2015, respectively	236	382	(1,111)	1,341
Foreign currency translation adjustment:
Foreign currency translation adjustment recognized during the period, net of tax of $(2) and $(44) for the three months ended and $32 and $(107) for the nine months ended in 2016 and 2015, respectively	(4)	(73)	52	(176)
Reclassification adjustment for loss on foreign currency translation adjustment included in net income (loss), net of tax of $0 and $0 for the three months ended and $0 and $491 for the nine months ended in 2016 and 2015, respectively	0	0	0	802
Foreign currency translation adjustment	(4)	(73)	52	626
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized loss on available-for-sale investments arising during the period, net of tax of $(23) and $(19) for the three months ended and $(35) and $(57) for the nine months ended in 2016 and 2015, respectively	(42)	(35)	(65)	(105)
Reclassification adjustment for loss on available-for-sale investments included in net income (loss), net of tax of $18 and $15 for the three months ended and $57 and $53 for the nine months ended in 2016 and 2015, respectively	33	28	106	98
Net unrealized gain (loss) on available-for-sale investments	(9)	(7)	41	(7)
Other comprehensive income (loss)	315	402	(743)	2,259
Comprehensive income (loss)	83,301	(148,824)	(133,731)	(693,770)
Loss from discontinued operations attributable to noncontrolling interest	0	(9,778)	(131,691)	(21,060)
Comprehensive income (loss) attributable to common stockholders	$ 83,301	$ (139,046)	$ (2,040)	$ (672,710)