Accumulated Other Comprehensive Income (Loss) (Reclassification) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net	$ (129)		$ (1,191)
Income before income tax expense	19,884		20,495
Income tax benefit (expense)	(6,257)		(5,915)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains and losses on marketable securities[Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net			323
Income tax benefit (expense)			(113)
Net income (loss)			210
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gain (loss) on derivative instruments [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net	145
Income tax benefit (expense)	(51)
Net income (loss)	94
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of defined benefit pension and other post-retirement benefit items [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Actuarial losses	412	[1]	214	[1]
Income before income tax expense	412		214
Income tax benefit (expense)	(144)		(75)
Net income (loss)	$ 268		$ 139

[1] 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.