Derivatives (Interest rate contracts designated as hedging instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Mar. 31, 2015
Interest Rate Fair Value Hedges [Abstract]
Interest rate contracts designated as hedging instruments	$ 19,958	$ 24,484

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=56946850&loc=SL5624163-113959

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