Retirement Plans - Pension Plan Asset Allocation (Details 7) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Retirement Plans
Target allocations	100.00%
Percentage of plan assets	100.00%	100.00%
Equity Securities
Retirement Plans
Target allocations	13.00%
Percentage of plan assets	11.00%	25.00%
Equity Securities \| Common Stock
Retirement Plans
Percentage of plan assets		6.00%
CTS common stock included in pension plan assets, Amount	$ 0	$ 17,700
Debt securities
Retirement Plans
Target allocations	83.00%
Percentage of plan assets	82.00%	59.00%
Other
Retirement Plans
Target allocations	4.00%
Percentage of plan assets	7.00%	16.00%

The amount of employer securities or securities of parties related to the employer that are included in plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (n)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- References

No definition available.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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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=82843861&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=82843861&loc=d3e1928-114920

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