Income Taxes - Reconciliation between Statutory Income Tax Rate and Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. Statutory Tax Rate	21.00%	21.00%	21.00%
Increase Due to State and Local Taxes	3.70%	4.20%	3.60%
Rate Benefits as a Limited Liability Company/Flow	(2.20%)	(2.50%)	(2.60%)
Foreign Taxes	(1.10%)	(0.10%)	0.20%
Non-Deductible Expenses(1)	0.70%	1.60%	1.20%
ASU 2016-09 Benefit for Stock Compensation	0.00%	(2.70%)	(4.20%)
Tax Cuts and Jobs Act - Primarily Related to the Re-measurement of Net Deferred Tax Assets	0.00%	0.00%	0.10%
Valuation Allowances	1.80%	0.30%	0.30%
Other Adjustments	(0.20%)	(0.60%)	0.10%
Effective Income Tax Rate	23.70%	21.20%	19.70%