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Income Taxes (Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate									21.00%	21.00%	35.00%
State taxes, net of federal tax benefit									2.40%	1.90%	1.30%
Foreign tax expense and tax rate differential									0.00%	(0.10%)	(1.10%)
Tax benefit from stock option exercises									(1.90%)	(3.80%)	(3.90%)
Enactment of the Tax Cuts and Jobs Act:
Re-measurement of deferred taxes									0.00%	0.00%	(4.90%)
One-time transition tax on repatriation of foreign earnings and withholding tax									0	(0.001)	0.026
Research and development tax credit									(1.10%)	(0.80%)	(0.90%)
Domestic Production Activities Deduction									0.00%	0.00%	(0.50%)
Foreign-Derived Intangible Income Deduction (FDII)									(0.20%)	(0.20%)	0.00%
Other, net									0.40%	(0.30%)	(0.20%)
Effective income tax rate	19.50%	18.90%	22.10%	22.10%	19.20%	18.60%	21.10%	11.90%	20.60%	17.60%	27.40%

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Effective Income Tax Rate Reconciliation,Tax Cuts And Jobs Act Of 2017, Foreign Derived Intangible Income Deduction, Percent

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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