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Common Shares (Activity Under ATM Share Offering Program) (Details) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 2010 ATM Program [Member]	Jun. 30, 2011 2010 ATM Program [Member]	Jun. 30, 2011 2011 ATM Program [Member]
Common shares sold	0.5			0.2	0.3	0.4
Total net consideration	$ 32,400	$ 37,126	$ 106,422	$ 10,000	$ 13,800	$ 23,300
Average price per share				$ 56.50	$ 55.81	$ 64.52

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- Definition

Average price per share offered under share offering program

+ Details

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- Definition

Common shares sold under ATM program.

+ Details

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X

- Definition

Value of new stock issued during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

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