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Pension and Other Postretirement Benefits - Schedule of Assumed Health Care Cost Trend Rates (Details) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Health care cost trend rate assumed for next year | 5.50% | 5.50% | 5.50%
Rate to which the cost trend rate gradually declines | 4.50% | 4.50% | 4.50%
Year that the rate reaches the rate at which it is assumed to remain | 2022 | 2021 | 2020
Number of years over actual annual healthcare cost trend experience | 20 years |  |
Minimum |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Rate to which the cost trend rate gradually declines | (3.30%) |  |
Maximum |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Rate to which the cost trend rate gradually declines | (0.50%) |  |
Other postretirement benefits |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Number of years over actual annual healthcare cost trend experience | 3 years |  |

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- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Year ultimate health care cost trend rate is expected to be reached, in CCYY format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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