Equity (Comprehensive Income) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Prior service cost	$ 525	$ 541
Unrecognized net actuarial loss	(8,639)	(8,703)
Fair value of derivatives, net of tax	369	(191)
Total accumulated other comprehensive income (loss)	$ (7,745)	$ (8,353)

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

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