Goodwill (Details) (USD $) In Thousands	6 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Goodwill [Roll Forward]
Goodwill	$ 1,654,242	$ 1,471,652
Accumulated impairment losses	(26,659)	(26,659)
Goodwill	1,444,993
Impairment loss	0
Acquisitions	181,780
Other/post acquisition adjustments	810
Goodwill	1,627,583
RP Data [Member] \| Data and Analytics [Member]
Goodwill [Roll Forward]
Acquisitions	162,882
Data and Analytics [Member]
Goodwill [Roll Forward]
Goodwill	913,864	750,172
Accumulated impairment losses	(19,734)	(19,734)
Goodwill	730,438
Impairment loss	0
Other/post acquisition adjustments	810
Goodwill	894,130
Business and Information Services [Member]
Goodwill [Roll Forward]
Goodwill	740,378	721,480
Accumulated impairment losses	(6,925)	(6,925)
Goodwill	714,555
Impairment loss	0
Other/post acquisition adjustments	0
Goodwill	733,453
Business and Information Services [Member] \| Dorado Network Systems [Member]
Goodwill [Roll Forward]
Acquisitions	18,898
Marketing Services Unit [Member]
Goodwill [Roll Forward]
Goodwill		123,300
Goodwill		$ 123,300

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ Details

- Definition

The increase (decrease) in the recorded value of goodwill for foreign currency translation adjustments and purchase accounting adjustments needed to revise the carrying amount of goodwill to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
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-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.

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-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.

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-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