Accumulated Other Comprehensive Income Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes	$ 39,901		$ 21,391
Income tax benefit	(13,872)		(9,079)
Net income	26,029		12,312
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Net income	(85)	[1]	(85)	[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]
Income (loss) before income taxes	(136)	[1]	(136)	[1]
Income tax benefit	51	[1]	51	[1]
Net income	$ (85)	[1]	$ (85)	[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).