Share-Based Compensation - Stock Options Activity (Details) - Stock Option - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Shares
Beginning balance (in shares)	1,386,539
Granted (in shares)	346,545
Exercised (in shares)	(171,636)
Forfeited/Expired (in shares)	(47,655)
Ending balance (in shares)	1,513,793	1,386,539
Vested and expected to vest (in shares)	1,416,714
Exercisable (in shares)	823,003
Weighted Average Price
Beginning Balance, Weighted Average Price (in dollars per share)	$ 103.58
Granted, Weighted Average Price (in dollars per share)	172.93
Exercised, Weighted Average Price (in dollars per share)	76.39
Forfeited, Weighted Average Price (in dollars per share)	140.09
Ending Balance, Weighted Average Price (in dollars per share)	$ 121.40	$ 103.58
Weighted-Average Remaining Contractual Term
Stock options outstanding, Weighted-Average Remaining Contractual Term	7 years 3 months 18 days	6 years 11 months 12 days
Aggregate Intrinsic Value
Stock options outstanding, Aggregate intrinsic value	$ 60,494,544	$ 94,764,140
Vested and expected to vest , Weighted Average Price (in dollars per share)	$ 62.92
Exercisable, Weighted Average Price (in dollars per share)	$ 96.53
Weighted-Average Remaining Contractual Term, Vested and expected to vest	7 years 2 months 8 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 1 month 6 days
Aggregate Intrinsic Value, Vested and expected to vest	$ 59,585,070
Aggregate Intrinsic Value, Exercisable	$ 51,004,523