Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Subsequent Event (Details) - CoBank, ACB [Member] - Common Class B [Member] - USD ($) $ in Millions	Feb. 19, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Common Stock Ownership Percentage by a Related Party		32.60%
Subsequent Event [Member]
Subsequent Event [Line Items]
Related Party Transaction, Purchases from Related Party	$ 546.0