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Income Taxes - Differences between Statutory Federal Income Tax Rate and Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal tax benefit	3.50%	3.20%	4.50%
Valuation allowance	0.10%	(0.60%)	0.00%
Tax planning benefits, excluding valuation allowance effects	0.00%	0.00%	(8.10%)
Tax reserves	(0.10%)	(0.40%)	(0.30%)
Tax credits	(0.30%)	(0.40%)	(0.30%)
Foreign tax rate effects	0.80%	0.40%	0.30%
Excess tax benefits from stock compensation activity	(2.90%)	(1.20%)	(0.80%)
Other, net	0.80%	(0.20%)	(0.30%)
Effective income tax rate	22.90%	21.80%	16.00%

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Effective Income Tax Rate Reconciliation, Tax Planning, Percent

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Effective Income Tax Rate Reconciliation Tax Reserves

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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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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 attributable to changes in the valuation allowance for deferred tax assets.

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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 attributable to other adjustments.

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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).

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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 attributable to research tax credit.

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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 attributable to foreign income tax settlement.

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