Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income (loss)	$ (229,804)	$ (237,358)	$ (215,974)	$ (546,803)
Net unrealized gain on derivative instruments qualifying as hedges:
Reclassification adjustment for loss on derivative instruments included in net loss, net of tax of $56 and $60 for the three months ended and $114 and $121 for the six months ended in 2016 and 2015, respectively	91	100	183	199
Postretirement liability adjustment:
Amortization of postretirement liability (gains) losses included in net periodic benefit cost, net of tax of $150 and $420 for the three months ended and $(819) and $649 for the six months ended in 2016 and 2015, respectively	248	584	(1,347)	959
Foreign currency translation adjustment:
Foreign currency translation adjustment recognized during the period, net of tax of $19 and $6 for the three months ended and $33 and $(63) for the six months ended in 2016 and 2015, respectively	31	9	56	(103)
Reclassification adjustment for loss on foreign currency translation adjustment included in net loss, net of tax of $0 and $0 for the three months ended and $0 and $491 for the six months ended in 2016 and 2015, respectively	0	0	0	802
Foreign currency translation adjustment	31	9	56	699
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 $(16) and $(23) for the three months ended and $(10) and $(34) for the six months ended in 2016 and 2015, respectively	(30)	(43)	(19)	(64)
Reclassification adjustment for loss on available-for-sale investments included in net loss, net of tax of $19 and $15 for the three months ended and $37 and $34 for the six months ended in 2016 and 2015, respectively	36	28	69	64
Net unrealized gain (loss) on available-for-sale investments	6	(15)	50	0
Other comprehensive income (loss)	376	678	(1,058)	1,857
Comprehensive loss	(229,428)	(236,680)	(217,032)	(544,946)
Loss from discontinued operations attributable to noncontrolling interest	(120,651)	(7,754)	(131,691)	(11,282)
Comprehensive loss attributable to common stockholders	$ (108,777)	$ (228,926)	$ (85,341)	$ (533,664)