Employee Benefit Plans (Details 2) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee benefits plans
Fair value of plan assets	$ 126,013	$ 116,725	$ 121,682
Total investments, excluding investments valued at NAV	$ 100,672	$ 83,194
Funded pension plan assets, by asset category (as a percent)	100.00%	100.00%
Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	$ 100,672	$ 83,194
Total investments, excluding investments valued at NAV	100,672	83,194
Equity Securities
Employee benefits plans
Fair value of plan assets	$ 80,191	$ 61,254
Funded pension plan assets, by asset category (as a percent)	64.00%	52.00%
Equity Securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	$ 80,191	$ 61,254
Debt Securities
Employee benefits plans
Fair value of plan assets	$ 20,481	$ 21,940
Funded pension plan assets, by asset category (as a percent)	16.00%	19.00%
Debt Securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	$ 20,481	$ 21,940
Other Securities
Employee benefits plans
Fair value of plan assets	$ 25,341	$ 33,531
Funded pension plan assets, by asset category (as a percent)	20.00%	29.00%

The total fair value of the plan investments before other items to reconcile to fair value of plan assets.

No definition available.

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- Definition

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+ References

No definition available.

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12355-114930

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Plan Assets
-URI http://asc.fasb.org/extlink&oid=6749337

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Plan Assets
-URI http://asc.fasb.org/extlink&oid=6520858

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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