Income Taxes (Effective Income Tax Rate Reconciliation) (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%	21.00%
State taxes, net of federal tax benefit	3.30%	2.60%	3.20%	2.60%
Foreign tax expense and tax rate differential	(0.20%)	(0.30%)	(0.10%)	(0.20%)
Tax benefit from stock option exercises	(0.40%)	(2.20%)	(1.00%)	(1.50%)
Expiration of the statute of limitations	(1.30%)	(1.20%)	(0.50%)	(0.40%)
Provision-to-return adjustment	(0.40%)	(0.60%)	(0.10%)	(0.20%)
Other, net	(0.60%)	(0.40%)	(0.50%)	(0.30%)
Effective income tax rate	21.40%	18.90%	22.00%	21.00%

Effective Income Tax Rate Reconciliation, Expiration Of The Statute Of Limitations, Percent

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Effective Income Tax Rate Reconciliation, Provision To Return Adjustments, Percent

+ References

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

+ References

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
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