Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Jurisdiction	Mar. 31, 2011
Income Taxes
Effective tax rate (as a percent)	26.80%	27.50%
Minimum number of tax jurisdictions	60
Liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	$ 22,535
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 3,900