Retirement Plans - Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Equity mutual funds
Defined Benefit Plans
Target allocation percentage of investments	12.00%
Fixed income mutual funds
Defined Benefit Plans
Target allocation percentage of investments	88.00%
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plans
Fair value of plan assets	$ 163.2	$ 162.7
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Cash
Defined Benefit Plans
Fair value of plan assets	0.6	0.6
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Equity mutual funds
Defined Benefit Plans
Fair value of plan assets	20.6	19.8
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fixed income mutual funds
Defined Benefit Plans
Fair value of plan assets	$ 142.0	$ 142.3

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ 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=49178875&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=58740216&loc=d3e1928-114920

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- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ 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)(i)
-URI http://asc.fasb.org/extlink&oid=58740216&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)(i)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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