Accumulated Other Comprehensive Loss - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes	$ 29,530		$ 28,387		$ 144,515		$ 97,990
Income tax benefit	(10,251)		(10,348)		(49,837)		(36,907)
Net income	19,279		18,039		94,678		61,083
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Net income	(85)	[1]	(85)	[1]	(255)	[1]	(255)	[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	(136)	[1],[2]	(136)	[1],[2]	(408)	[1],[2]	(408)	[1],[2]
Income (loss) before income taxes	(136)	[1]	(136)	[1]	(408)	[1]	(408)	[1]
Income tax benefit	51	[1]	51	[1]	153	[1]	153	[1]
Net income	$ (85)	[1]	$ (85)	[1]	$ (255)	[1]	$ (255)	[1]

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

[2] This accumulated other comprehensive income component is included in the computation of net periodic benefit cost (see Note 6. Employee Benefit Plans footnote for additional details).