Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes
Statutory federal tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefit	2.50%	2.60%	2.10%
Release of valuation allowance		(2.90%)
Federal research & development credits	(0.70%)	(2.10%)	(0.60%)
Other permanent differences	0.10%	0.50%	0.10%
Effective tax rate	22.90%	19.10%	22.60%