Debt - Rural Utilities Service Guaranteed Loans (Details) - USD ($)	1 Months Ended	6 Months Ended
Apr. 30, 2019	Jun. 30, 2019
Long-term debt \| FFB \| Rural Utilities Service Guaranteed Loans
Debt
Advances received on loans	$ 25,022,000	$ 72,986,000

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

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