Pension Plans and Other Postretirement Benefits Defined Benefit Plan Asset Target Allocation (Details) - Pension Plans	Dec. 31, 2017
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocations percentage of assets	43.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target allocations percentage of assets	44.00%
Absolute return
Defined Benefit Plan Disclosure [Line Items]
Target allocations percentage of assets	13.00%

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.

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

Name:	us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant