Pension and Savings Plans (Details 5) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Corporate Debt Securities [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	$ 259.4
Assets Held At Reporting Date:
Fair value of plan assets at end of period	$ 265.7	$ 259.4
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust	2.00%	3.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust		31.00%
Fixed Income Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust		69.00%
Real Estate Investment [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	$ 23.0
Assets Held At Reporting Date:
Fair value of plan assets at end of period	14.1	$ 23.0
Private Equity Funds [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	183.9
Assets Held At Reporting Date:
Fair value of plan assets at end of period	186.1	183.9
Banks, Trust and Insurance, Equities [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	97.3
Assets Held At Reporting Date:
Fair value of plan assets at end of period	109.0	97.3
Fair Value, Inputs, Level 2 [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	301.0
Assets Held At Reporting Date:
Fair value of plan assets at end of period	301.0	301.0
Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	259.4
Assets Held At Reporting Date:
Fair value of plan assets at end of period	265.7	259.4
Fair Value, Inputs, Level 2 [Member] \| Real Estate Investment [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	0.0
Assets Held At Reporting Date:
Fair value of plan assets at end of period	0.0	0.0
Level 3 [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	23.0
Assets Held At Reporting Date:
Fair value of plan assets at end of period	14.1	23.0
Level 3 [Member] \| Corporate Debt Securities [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	0.0
Assets Held At Reporting Date:
Fair value of plan assets at end of period	0.0	0.0
Level 3 [Member] \| Real Estate Investment [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	23.0	30.2
Assets Held At Reporting Date:
Realized gains	1.8	3.2
Unrealized gains relatng to investments still held at the reporting date	0.2	0.2
Purchases, sales and settlements, net	(10.9)	(10.6)
Fair value of plan assets at end of period	14.1	23.0
Pension Plans, Defined Benefit [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	757.3	839.8
Assets Held At Reporting Date:
Fair value of plan assets at end of period	$ 773.0	$ 757.3

Assets held at the reporting date.

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- Definition

Defined benefit plan actual return on plan assets unrealized during period.

+ References

No definition available.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ 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)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

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

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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.

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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

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from purchases, sales and settlements.

+ 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)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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