Loans and Allowance for Losses - Narrative (Details) $ in Millions	Feb. 19, 2019 USD ($)
Purchase of Loans [Member] \| CoBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of portfolio of participations in season Rural Utilities loans	$ 546.2

The cash outflow for the purchase of loan receivable arising from the financing of goods and services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireLoansReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration