Stock-Based Compensation - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Shares
Award contractual life	10 years
2013 Equity Incentive Plan
Shares
Annual forfeiture rate	0.31%
Expected forfeiture rate over contractual term	3.10%
2013 and 2018 Equity Incentive Plans
Shares
Outstanding, beginning balance (in shares)	287,990
Less exercised (in shares)	14,398
Forfeited or Expired, Shares	0
Outstanding, ending balance (in shares)	335,877	287,990
Expected to vest, assuming a 0.31% annual forfeiture rate (in shares)	334,824
Exercisable (in shares)	174,988
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 36.98
Granted (in dollars per share)	42.70
Less exercised (in dollars per share)	16.89
Forfeited or expired, Weighted-Average Exercise Price (in dollars per share)	0
Outstanding, ending balance (in dollars per share)	38.90	$ 36.98
Expected to vest, assuming a 0.31% annual forfeiture rate (in dollars per share)	38.87
Exercisable (in dollars per share)	$ 28.62
Weighted-Average Remaining Contractual Term In Years
Outstanding, beginning balance		6 years 9 months 7 days
Granted	6 years 5 months 12 days
Outstanding, ending balance	6 years 6 months 29 days
Expected to vest, assuming a 0.31% annual forfeiture rate, Weighted Average Remaining Contractual Term	6 years 6 months 29 days
Exercisable	4 years 8 months 8 days
Aggregate Intrinsic Value
Beginning balance	$ 7,722,369
Less exercised	453,674
Forfeited or Expired, Aggregate Intrinsic Value	0
Ending balance	5,721,159	$ 7,722,369
Expected to vest, assuming a 0.31% annual forfeiture rate	5,713,654
Exercisable	$ 4,733,571