Accumulated Other Comprehensive Loss Reclassification Adjustment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Interest Expense	$ (31,420)		$ (29,234)		$ (30,330)
Derivatives, reclassification adjustment for amounts recognized in net income, tax	(114)		(132)		(230)
Net prior service benefit amortization (net of tax of $(146) and $(308), respectively)	236		493		160
Net prior service benefit amortization, tax	146		308		99
Net actuarial loss amortization, tax	(1,231)		(5,762)		(6,544)
Net actuarial losses recognized during the year (net of tax of $(1,231), $(5,762) and $(6,544), respectively)	(1,996)		(9,130)		(10,721)
Available for sale securities, reclassification adjustment for amounts recognized in net income, tax	(29)		(19)		0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Total reclassifications for the period	(601)		20,702
Interest Rate Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest Expense	(213)		(192)
Derivatives, reclassification adjustment for amounts recognized in net income, tax	(114)		(132)
Pension and Other Post-retirement Benefits | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net prior service benefit amortization (net of tax of $(146) and $(308), respectively)	(236)	[1]	(493)	[1]
Net prior service benefit amortization, tax	146		308
Prior service cost occurring during the year, tax	0		(803)
Net actuarial loss amortization, tax	(1,231)		(5,762)
Settlements, tax	0		(7,799)
Net actuarial losses recognized during the year (net of tax of $(1,231), $(5,762) and $(6,544), respectively)	1,996	[1]	9,130	[1]
Prior service cost recognized due to curtailment (net of tax of $0, $(803) and $0, respectively	0		1,272	[1]
Settlements (net of tax of $0 and $7,799, respectively)	0		(12,357)	[1]
Amounts reclassified from AOCI	1,760		22,266
Unrealized Gain on Securities, Net | Reclassification out of Accumulated Other Comprehensive Income [Member]
Investment Income, Net	(2,148)		(1,372)
Available for sale securities, reclassification adjustment for amounts recognized in net income, tax	$ (29)		$ (19)

[1] Pension and other post-retirement benefits AOCI components are included in the computation of net periodic benefit cost (refer to note 13 to the consolidated financial statements).