Income Taxes (Narrative) (Details) - Deltic MDF Facility [Member] $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Income Taxes [Line Items]
Reduction to deferred tax liabilities	$ (15.8)
Increase to income taxes payable	$ 15.8

The increase (decrease) during the reporting period in the amounts payable to taxing authorities for taxes that are based on the reporting entity's earnings, net of amounts receivable from taxing authorities for refunds of overpayments or recoveries of income taxes, and in deferred and other tax liabilities and assets.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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