Accumulated Other Comprehensive Income (Loss) (Reclassification) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)									$ 0		$ 0		$ (3,245)
Income tax expense (benefit)									(27,527)		(11,226)		46,484
Income (loss) from continuing operations	7,013	20,388	10,902	14,580	11,528	13,572	5,583	6,976	52,883		37,659		69,134
Income (loss) before income taxes									80,410		48,885		22,650
Amounts reclassified from accumulated other comprehensive income (loss) for the period ended December 31, 2013 [Member] | Unrealized gain (loss) on derivative instruments [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)									321		363
Income tax expense (benefit)									(112)		(127)
Income (loss) from continuing operations									209		236
Amounts reclassified from accumulated other comprehensive income (loss) for the period ended December 31, 2013 [Member] | Amortization of defined benefit pension and other post-retirement benefit items: [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)									(2,102)		(1,838)
Income (loss) from continuing operations									3,904		3,412
Prior service costs									0	[1]	1,431	[2]
Actuarial losses									6,006	[1]	3,819	[2]
Income (loss) before income taxes									$ 6,006		$ 5,250

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See Note 9 - "Pension Benefits and Retirement Health and Life Insurance Benefits" for additional details.

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See Note 9 - "Pension Benefits and Other Postretirement Benefit Plans" for additional details.