Accumulated Other Comprehensive Loss - Schedule of Reclassifications Out of 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
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes		$ (2,455)	$ 29,530	$ 52,950	$ 144,515
Income tax provision (benefit)		(1,505)	10,251	17,556	49,837
Net income		(950)	19,279	35,394	94,678
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]	(85)	(85)	(255)	(255)
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]	(136)	(136)	(408)	(408)
Income (loss) before income taxes	[1]	(136)	(136)	(408)	(408)
Income tax provision (benefit)	[1]	51	51	153	153
Net income	[1]	$ (85)	$ (85)	$ (255)	$ (255)

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

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