Share-Based Compensation - Stock Options Activity (Details) - Stock Option - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Shares
Beginning balance (in shares)	1,386,539
Granted (in shares)	341,285
Exercised (in shares)	(27,978)
Forfeited/Expired (in shares)	(22,665)
Ending balance (in shares)	1,677,181	1,386,539
Vested and expected to vest (in shares)	1,214,651
Exercisable (in shares)	562,925
Weighted Average Price
Beginning Balance, Weighted Average Price (in dollars per share)	$ 103.58
Granted, Weighted Average Price (in dollars per share)	173.31
Exercised, Weighted Average Price (in dollars per share)	74.68
Forfeited, Weighted Average Price (in dollars per share)	131.64
Ending Balance, Weighted Average Price (in dollars per share)	$ 117.88	$ 103.58
Weighted-Average Remaining Contractual Term
Stock options outstanding, Weighted-Average Remaining Contractual Term	7 years 4 months 9 days	6 years 11 months 12 days
Aggregate Intrinsic Value
Stock options outstanding, Aggregate intrinsic value	$ 48,014,239	$ 94,764,140
Vested and expected to vest , Weighted Average Price (in dollars per share)	$ 80.14
Exercisable, Weighted Average Price (in dollars per share)	$ 80.05
Weighted-Average Remaining Contractual Term, Vested and expected to vest	4 years 9 months 10 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 4 months 17 days
Aggregate Intrinsic Value, Vested and expected to vest	$ 36,239,484
Aggregate Intrinsic Value, Exercisable	$ 32,686,084