Supplementary Data on Cash Flows (Details 2) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2017	Dec. 31, 2017
Effect of Tax Cuts and Jobs Act of 2017
Increase in income tax expense		$ 10,095
Tax Cuts and Jobs Act of 2017
Effect of Tax Cuts and Jobs Act of 2017
Increase in income tax expense	$ 10,100	10,100
Increase in income tax expense due to re-measurement of net deferred tax assets		19,900
Deferred tax benefit related to acceleration of pension contributions		$ (9,800)

Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration