Income Taxes (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013 item	Sep. 30, 2012
Income Taxes
Effective tax rate (as a percent)	23.90%		26.80%	23.90%	26.80%
Tax benefit primarily related to the completion of prior audits	$ 3,645			$ 3,645
Tax benefit per diluted common share primarily related to the completion of prior audits (in dollars per share)	$ 0.02			$ 0.02
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
Tax benefit per diluted common share 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 (in dollars per share)		$ 0.07
Effective tax rate before adjustments (as a percent)	25.50%			26.30%
Minimum number of tax jurisdictions				60
Liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	13,109			13,109
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 2,221			$ 2,221