Statements of Shareholders' Equity (Parentheticals) - $ / shares	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Additional Paid-in Capital [Member]
Cash dividends declared per common share (in dollars per share)	$ 4	$ 4	$ 2.06

Aggregate dividends paid during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration