Consolidated Statements Of Income And Retained Earnings (Parenthetical) (USD $)	3 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements Of Income And Retained Earnings
Common stock, cash dividends declared per share	$ 0.48	$ 0.47
Series B, preferred stock dividend rate	6.75%	6.75%

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 2: 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=6959260&loc=d3e187085-122770

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Namespace Prefix:	us-gaap
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration