Goodwill (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Jun. 30, 2013 International	Jun. 30, 2013 North America	Dec. 31, 2012 North America
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 276,599	$ 142,918	$ 133,681	$ 133,681
Effect of foreign exchange rate changes	(4,041)	(4,041)
Balance at the end of the period	$ 272,558	$ 138,877	$ 133,681	$ 133,681

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 2: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Reference 8: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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