Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 145,765	$ 27,858	$ (4,705)	$ 61,010
Change in unrecognized benefit plan losses arising during the period, net of taxes of $1,303 for the three months ended September 30, 2015, and $2,367 and $(434) for the nine months ended September 30, 2016 and September 30, 2015, respectively	0	2,021	3,671	(673)
Adjustment for previously unrecognized benefit plan gains and losses included in net income, net of taxes of $(28) and $2 for the three months ended September 30, 2016 and September 30, 2015, respectively, and $(85) and $7 for the nine months ended September 30, 2016 and September 30, 2015, respectively	(44)	4	(132)	11
Change in unrecognized benefit plan gains and losses, net of taxes	(44)	2,025	3,539	(662)
Change in unrealized holding gain arising during the period, net of taxes of $341 and $(1,152) for three months ended September 30, 2016 and September 30, 2015, respectively, and $1,026 and $(2,340) for the nine months ended September 30, 2016 and September 30, 2015, respectively	593	(1,785)	1,591	(3,628)
Change in foreign currency translation adjustments, net of taxes of $(103) and $(741) for the three months ended September 30, 2016 and September 30, 2015, respectively, and $(1,198) and $(1,148) for the nine months ended September 30, 2016 and September 30, 2015, respectively	2,135	(4,011)	2,002	(8,879)
Other Comprehensive Income (Loss), net of taxes	2,684	(3,771)	7,132	(13,169)
Comprehensive Income	$ 148,449	$ 24,087	$ 2,427	$ 47,841