Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012
Income Taxes
Effective tax rate (as a percent)	20.90%	26.80%
Tax cost primarily related to delay of research and development credits and certain domestic taxes on foreign income that are part of tax provisions within American Taxpayer Relief Act	$ 11,300
Net income per diluted common share resulting from the delay in the reinstatement of certain federal income tax provisions for the year 2012	$ 0.07
Effective tax rate before adjustments (as a percent)	26.80%
Minimum number of tax jurisdictions	60
Liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	17,149,000
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 5,764,000