Shareholders' Equity Reclassifications from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs		$ (15)	$ (15)
Actuarial losses		(327)	(497)
Income Before Income Taxes		19,410	10,883
Tax benefit (provision)		(8,626)	(5,030)
Net income		10,784	5,853
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]	239	(505)
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]	15	(15)
Actuarial losses	[1],[2]	327	(497)
Settlement and Other	[1],[2]	0	0
Income Before Income Taxes	[1]	342	(512)
Tax benefit (provision)	[1]	(103)	7
Net income	[1]	$ 239	$ (505)

[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.