Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Income Tax Contingency [Line Items]
Income tax provision	$ 31,769,000	$ 41,714,000	$ 38,777,000	$ 82,985,000
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Effective tax rate	35.50%	26.50%	34.40%	25.30%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate			35.00%
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations			3,800,000
Possible decrease in gross unrecognized tax benefits within next 12 months	2,800,000		2,800,000
Foreign Country [Member]
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Number of ongoing tax examinations	2		2
Interest and penalties recorded	$ 4,600,000		$ 4,600,000