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Income Taxes and Related Payments - Reconciliation of effective tax rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	21.00%	21.00%	21.00%
State and local taxes, net of federal tax effect	3.10%	2.80%	2.10%
Excess tax benefits on share-based compensation	(1.10%)	(0.70%)	(0.40%)
Rate benefit from the flow through entity	(5.50%)	(6.70%)	(6.70%)
Change in state tax rate	(1.10%)	(6.80%)	0.00%
Unrecognized tax benefits	0.20%	0.60%	0.00%
Other	(0.10%)	0.10%	(0.20%)
Effective tax rate	16.50%	10.30%	15.80%

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Tax Rate Reconciliation Rate Benefit From Flow Through Entity 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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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 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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