Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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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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Employee Retirement Plans - Estimated fair value of plan assets and target asset allocations - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Actual Allocation	100.00%
Fair Value Measurement	$ 488.0	$ 442.5	$ 422.8
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	7.3	5.9
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	480.7	436.6
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	$ 0.0	0.0
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%
Actual Allocation	2.00%
Fair Value Measurement	$ 7.3	5.9
Cash and cash equivalents \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	7.3	5.9
Cash and cash equivalents \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	0.0	0.0
Cash and cash equivalents \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	$ 0.0	0.0
Liability hedging portfolio
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	50.00%
Actual Allocation	44.00%
Growth portfolio
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	50.00%
Actual Allocation	54.00%
Debt common trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	$ 292.8	277.2
Debt common trust funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	0.0	0.0
Debt common trust funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	292.8	277.2
Debt common trust funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	0.0	0.0
Equity common trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	187.9	159.4
Equity common trust funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	0.0	0.0
Equity common trust funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	187.9	159.4
Equity common trust funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value Measurement	$ 0.0	$ 0.0