Net Income Per Share (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock options and stock settled appreciation rights (SSARs) excluded from calculation of diluted shares			25,000	249,000
Purchased restricted stock outstanding as a percentage of common stock			0.60%	0.60%
Net income allocated to PRS	$ 0.4	$ 0.4	$ 1.0	$ 0.8
Maximum [Member]
Difference between basic and diluted net income per share			$ 0.01	$ 0.01

The difference between basic and diluted net income per share for both common shareholders and PRS shareholders.

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- Definition

Aggregate of earnings distributed and earnings allocated to participating securities under the two-class method to the extent that participating securities may share in earnings as if all of the earnings for the period had been distributed.

+ Details

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- Definition

Purchased Restricted Stock Outstanding As A Percentage Of Common Stock

+ Details

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- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would increase EPS amounts or decrease loss per share amounts for the period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 13, 14

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 171

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 40
-Subparagraph c

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration