Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	6 Months Ended
Jun. 30, 2017 USD ($)
Derivative instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	$ 0
Unrealized gains (losses)	276
Amounts reclassified from AOCI	0
Ending Balance	276
Pension, Postretirement and Other Postemployment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	24,067
Unrealized gains (losses)	3,641
Amounts reclassified from AOCI	(487)
Ending Balance	27,221
Available-for-sale securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	387
Unrealized gains (losses)	(55)
Amounts reclassified from AOCI	(332)
Ending Balance	0
Accumulated Other Comprehensive Income
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	24,454
Unrealized gains (losses)	3,862
Amounts reclassified from AOCI	(819)
Ending Balance	$ 27,497

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581

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- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4I
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4568740-111683

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-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4568447-111683

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