Income Taxes - Income tax rate reconciliation (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%
Non-deductibility of goodwill impairment	(17.90%)	0.00%	0.00%
State and other taxes, net of federal tax benefit	1.20%	2.80%	3.60%
Change in unrecognized tax benefits	2.00%	1.80%	3.30%
Change in valuation allowance	(1.50%)	0.50%	0.40%
Changes in tax rates and state tax laws	(0.40%)	(0.50%)	(1.60%)
Change in accounting for excess tax deficiencies/benefits	0.10%	(0.60%)	0.10%
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	0.80%	(1.30%)	(0.20%)
Other	(1.10%)	0.90%	0.80%
Effective tax rate	4.20%	24.60%	27.40%