Goodwill (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended			9 Months Ended
Sep. 30, 2013	Sep. 30, 2013 Region One	Sep. 30, 2013 Region Two	Dec. 31, 2012 Region Two	Sep. 30, 2013 Region Three	Sep. 30, 2013 Region Four	Dec. 31, 2012 Region Four	Sep. 30, 2013 Region Five	Dec. 31, 2012 Region Five
Changes in carrying amounts of goodwill
Balance at the beginning of the period	$ 439,486	$ 193,758	$ 32,245	$ 32,245	$ 66,181	$ 62,621	$ 62,621	$ 84,681	$ 84,681
Contingent payments related to acquisitions	93	93
Foreign currency translation	(197)				(197)
Balance at the end of the period	$ 439,382	$ 193,851	$ 32,245	$ 32,245	$ 65,984	$ 62,621	$ 62,621	$ 84,681	$ 84,681

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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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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