Income Taxes - Difference of Income Taxes from Statutory Federal Income Tax Rates (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal U.S. income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal tax benefit	4.90%	4.90%	4.70%
Permanent book/tax differences	0.30%	0.50%	0.20%
Compensation book/tax differences	1.30%	0.60%	0.40%
Non-U.S. income taxed at different rates, net of foreign tax credits	1.70%	2.10%	2.00%
Federal tax credits	(1.50%)	(1.40%)	(1.70%)
Tax impact of uncertain tax positions	0.10%	0.20%	0.80%
Tax effects of TCJA	0.00%	0.00%	0.40%
Other, net	(0.40%)	(0.50%)	(1.20%)
Effective tax rate	27.40%	27.40%	26.60%