Derivatives (Interest rate contracts designated as hedging instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Interest Rate Fair Value Hedges [Abstract]
Assets	$ 359	$ 437
Liabilities		$ (897)

Fair value as of the balance sheet date of all derivative liabilities designated as interest rate fair value hedging instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

Name:	us-gaap_InterestRateFairValueHedgeLiabilityAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant