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Pension Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months			$ 98.0
Defined contribution plan- Company contribution (percent)			6.50%
Defined contribution plan- Company matching contribution (percent)			3.00%
Other postretirement benefit costs for a defined contribution plan			$ 41.2	$ 21.9	$ 24.3
Projected future contributions to VEBA trusts			$ 7.0
US Qualified Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of total assets			96.00%
Number of shares of equity securities issued by employer included in plan assets			3.0	3.0
Fair value of employer equity securities included in plan assets			$ 33.2	$ 102.7
Dividends on employer stock received by plan			1.8	2.1
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months			64.0
One-time, voluntary lump sum payments				52.0
Benefit obligation increase for changes in mortality assumptions				$ 90.0
Weighted average life expectancy				18 years
Average remaining service period				10 years
Accumulated benefit obligation			$ 2,767.0	$ 2,917.3
Expected long-term rate of return on assets			8.00%	8.25%	8.25%
Actual return on plan assets	0.30%		(1.20%)	6.50%	14.30%	8.00%
Fair value of plan assets			$ 1,962.3	$ 2,204.4	$ 2,329.8
Other Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated employer contributions in next 12 months			10.0
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months			$ 34.0
Assumed increase in per capita cost of covered benefits in next 12 months			8.00%
Assumed ultimate health care cost trend rate			4.50%
Year that ultimate trend rate is reached			2038
Expected long-term rate of return on assets			4.00%	8.30%	8.30%
Fair value of plan assets			$ 1.8	$ 2.9	$ 4.0
Private equity [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets			201.2	172.6
Fair Value, Inputs, Level 3 [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets			800.2	809.7	655.3
Fair Value, Inputs, Level 3 [Member] | Private equity [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets			201.2	172.6	123.0
Fair Value, Inputs, Level 3 [Member] | Private equity [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets			$ 1.8
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other postretirement benefit costs for a defined contribution plan				$ 2.6	$ 4.6
Forecast [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on assets		8.00%
Forecast [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on assets		4.00%
MultiemployerPlan1 [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of Current Year Contributions to Plan that Company Contributions Exceed				5.00%

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The actual investment return on assets of defined benefit plans in percentage terms

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Defined Benefit Plan Actuarial Net Gains Losses Mortality Change

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Defined Benefit Plan, Weighted Average Life Expectancy

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Defined Contribution Plan, Employers Contribution

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Percent of Current Year Contributions to Plan that Company Contributions Exceed

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For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6503844

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

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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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.

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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Changes in the defined benefit obligation, not otherwise separately disclosed in the financial statements.

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The ultimate trend rate for health care costs.

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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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