Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Jan. 31, 2020	Jun. 30, 2019	Jan. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 02, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Common stock, par value (USD per share)				$ 0.001		$ 0.001		$ 0.001	$ 0.001
Aggregate offering price								$ 200,000
Stock issued in transaction (shares)	3,538,462	2,415,000	1,854,838
Sale price of common stock (USD per share)	$ 97.50		$ 62.00		$ 97.00		$ 97.00
Proceeds from sale of stock	$ 324,000	$ 219,900	$ 107,900
Stock issued pursuant to stock option exercises (shares)				272,158	91,257	1,092,468	424,144
Proceeds from stock options exercised				$ 12,400	$ 1,100	$ 36,300	$ 5,400
Proceeds from disgorgement of shareholders' short-swing profits			$ 1,100			$ 41	$ 1,050