Business Combinations (Results Of Operations) (Details) (USD $) In Thousands, except Share data	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
Jun. 30, 2010 2010 Acquisition [Member]	Jun. 30, 2009 2010 Acquisition [Member]	Jun. 30, 2010 2010 Acquisition [Member]	Jun. 30, 2009 2010 Acquisition [Member]	Jun. 30, 2011 2011 Acquisitions [Member]	Jun. 30, 2010 2011 Acquisitions [Member]	Jun. 30, 2011 2011 Acquisitions [Member]	Jun. 30, 2010 2011 Acquisitions [Member]
Total revenues	$ 244,250	$ 251,915	$ 500,743	$ 520,953	$ 249,183	$ 254,929	$ 518,557	$ 519,985
Income before income taxes	68,203	68,741	142,671	149,698	62,194	71,539	140,929	148,573
Net income	$ 41,300	$ 41,738	$ 86,265	$ 90,811	$ 37,473	$ 43,320	$ 85,011	$ 89,833
Net income per share, basic	$ 0.29	$ 0.29	$ 0.61	$ 0.64	$ 0.26	$ 0.30	$ 0.60	$ 0.63
Net income per share, diluted	$ 0.29	$ 0.29	$ 0.60	$ 0.64	$ 0.26	$ 0.30	$ 0.58	$ 0.63
Weighted average number of shares outstanding, basic	137,685	136,939	137,654	136,937	138,379	137,685	138,365	137,654
Weighted average number of shares outstanding, diluted	139,105	137,304	138,937	137,261	139,942	139,105	140,950	138,937

Business acquisition, pro forma earnings per share, weighted average number of basic shares outstanding.

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- Definition

Business acquisition, pro forma earnings per share, weighted average number of shares outstanding, diluted.

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- Definition

The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect per basic share of common stock for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=6909870&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 54
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 55
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 68
-Subparagraph r(2, 3)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, per diluted share of common stock for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

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