Shareholders' Equity Reclassifications from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		$ 0	$ 962	$ (1,407)	$ 962
Prior-service costs		(16)	(14)	(47)	(43)
Actuarial losses		(330)	(488)	(991)	(1,470)
Income Before Income Taxes		4,528	23,202	56,633	24,569
Tax benefit (provision)		(13,430)	(9,932)	(34,249)	(19,060)
Net income		(8,902)	13,270	22,384	5,509
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	[1],[2]	16	(14)	47	(43)
Actuarial losses	[1],[2]	330	(488)	991	(1,470)
Settlement and Other	[1],[2]	498	(375)	488	(375)
Income Before Income Taxes	[1]	844	(877)	1,526	(1,888)
Tax benefit (provision)	[1]	(272)	11	(432)	24
Net income	[1]	$ 572	$ (866)	$ 1,094	$ (1,864)

[1] Amounts in parentheses indicate debits to the Consolidated Statements of Operations.

[2] These AOCI components are included in the computation of net periodic pension cost. Refer to Note 8 for additional details.