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Postretirement Health Care and Life Insurance Benefits (Details 3) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Postretirement Health Care and Life Insurance Benefits [Member] |  |  |  |
Weighted-average assumptions used to determine benefit obligations |  |  |  |
Discount rate |  | 4.15% | 4.50% |
Measurement date |  | Dec. 31, 2016 | Dec. 31, 2015 |
Weighted-average assumptions used to determine net periodic benefit cost |  |  |  |
Discount rate |  | 4.50% | 4.10% | 4.90%
Measurement date |  | December 31, 2015 | December 31, 2014 | December 31, 2013
Assumed health care cost trend rates, One percentage point increase |  |  |  |
One Percentage-Point Increase Effect on total service and interest cost components | [1] | $ 3.6 |  |
One Percentage-Point Decrease Effect on total service and interest cost component | [1] | (3.2) |  |
One Percentage-Point Increase Effect on total postretirement benefit obligation | [1] | 67.0 |  |
One Percentage-Point Decrease Effect on total postretirement benefit obligation | [1] | $ (61.9) |  |
Pre-Medicare [Member] |  |  |  |
Assumed health care cost trend rate |  |  |  |
Health care cost trend rate assumed for next year |  | 6.20% | 6.60% |
Rate to which the cost trend is assumed to decline (the ultimate trend rate) |  | 4.75% | 4.75% |
Year that the rate reaches the ultimate trend rate |  | 2021 | 2021 |
Post-Medicare [Member] |  |  |  |
Assumed health care cost trend rate |  |  |  |
Health care cost trend rate assumed for next year |  | 5.60% | 5.80% |
Rate to which the cost trend is assumed to decline (the ultimate trend rate) |  | 4.75% | 4.75% |
Year that the rate reaches the ultimate trend rate |  | 2021 | 2021 |
[1] | In addition to the effect on total service and interest cost components of expense, changes in trend rates would also increase or decrease the actuarial gain or loss amortization expense component. The impact on actuarial gain or loss amortization would approximate the increase or decrease in the obligation divided by 10.31 years at January 1, 2017.

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- Definition The interest rate used to adjust for the time value of money for the 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The measurement date for determining rate assumptions used in calculating the net periodic benefit cost (such as the weighted-average expected long-term rate of return on plan assets and the discount rate) is normally the beginning of the year measurement date. If an assumed rate(s) changes due to a subsequent interim measurement of both plan assets and obligations, disclosure of the beginning and more recently assumed rate(s), or a properly weighted combination of the two. Disclosure may include the more recent measurement date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2919-114920 + Details
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- Definition The interest rate used to adjust for the time value of money. + 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=58740216&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 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=58740216&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 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=58740216&loc=d3e1928-114920 + 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 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=58740216&loc=d3e1928-114920 + 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 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=58740216&loc=d3e1928-114920 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Health Care Cost Trend Rate -URI http://asc.fasb.org/extlink&oid=6514820 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The ultimate trend rate for health care costs. + 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 (l) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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