Shareholders' Equity Reclassifications from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		$ 962	$ 0	$ 962	$ 0
Prior-service costs		(14)	(17)	(43)	(53)
Actuarial losses		(488)	(118)	(1,470)	(363)
Income before income taxes		23,469	12,037	24,897	38,958
Tax benefit (provision)		(10,144)	(4,484)	(19,673)	(11,679)
Net income		13,325	7,553	5,224	27,279
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]	(866)	(98)	(1,864)	(314)
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]	(14)	(17)	(43)	(53)
Actuarial losses	[1],[2]	(488)	(118)	(1,470)	(363)
Settlement and Other	[1],[2]	(375)	(6)	(375)	(35)
Income before income taxes	[1]	(877)	(141)	(1,888)	(451)
Tax benefit (provision)	[1]	11	43	24	137
Net income	[1]	$ (866)	$ (98)	$ (1,864)	$ (314)

[1] Amounts in parenthesis 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.