Accumulated Other Comprehensive Loss - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015		Jun. 30, 2016	Jun. 30, 2015
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes		$ 23,109		$ 50,367		$ 201	$ 55,405
Income tax provision (benefit)		7,668		17,969		382	19,061
Net income (loss)		15,441		32,398		(181)	36,344
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)		(56)	[1]	(85)	[1]	(238)	(170)	[1]
Defined Benefit Plan Items | Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior-service cost	[1],[2]	(89)		(136)		(177)	(272)
Income (loss) before income taxes	[1]	(89)		(136)		(177)	(272)
Income tax provision (benefit)	[1]	33		51		65	102
Net income (loss)	[1]	(56)		$ (85)		(112)	$ (170)
Gain on sale of investment | Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Recognition of gain on sale of investment	[1]	0				(200)
Income (loss) before income taxes	[1]	0				(200)
Income tax provision (benefit)	[1]	0				74
Net income (loss)	[1]	$ 0				$ (126)

[1] Amounts in parentheses indicate credits to profit/loss

[2] This accumulated other comprehensive loss component is included in the computation of net periodic benefit cost (see Note 6).