Income Taxes (Schedule of Effective Tax Rate Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. statutory federal rate applied to pretax income	21.00%	21.00%	21.00%
State and local income taxes, net of federal benefit	4.30%	3.20%	4.20%
Foreign tax rate differential	(0.20%)	0.20%	1.50%
Non-deductible expenses	1.50%	1.70%	1.70%
Goodwill and intangible assets	(0.20%)	(0.50%)	3.60%
Change in tax rate	0.60%	(1.50%)	(2.80%)
Other	(0.60%)	(1.00%)	(2.40%)
Tax credits	(1.20%)	(0.60%)	(0.40%)
Stock basis adjustment	0.00%	(1.80%)	0.00%
Valuation allowance for deferred tax assets	(1.10%)	2.20%	2.60%
Effective income tax rate	24.10%	22.90%	29.00%