Employee plans - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Compensation and Retirement Disclosure [Abstract]
Effect on service and interest cost, 1-Percentage-Point Increase	$ 0.2
Effect on postretirement benefit obligation, 1-Percentage-Point Increase	2.6
Effect on service and interest cost, 1-Percentage-Point Decrease	(0.2)
Effect on postretirement benefit obligation, 1-Percentage-Point Decrease	$ (2.4)

No definition available.

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ 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 (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

+ Details

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

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