Earnings Per Share (Narratives) (Details) - shares	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Employee stock ownership plan, unreleased shares	17,581	20,226	21,883

Number of employee stock ownership plan (ESOP) shares that have not been committed to be released determined by relating the portion of time within a reporting period that these shares have been outstanding to the total time in that period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65882273&loc=d3e17400-113927

Name:	us-gaap_WeightedAverageNumberOfSharesEmployeeStockOwnershipPlanSharesNotCommittedToBeReleased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration