Derivatives (Interest rate contracts designated as hedging instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Interest Rate Fair Value Hedges [Abstract]
Interest rate contracts designated as hedging instruments	$ 1,253	$ 4,903

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

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